❤️ Okun's law 🦚

"Graph of US quarterly data (not annualized) from 1948 through 2016 estimates a form of the difference version of Okun's law: %Change GDP = 3.2 - 1.8*(Change Unemployment Rate). R^2 of .463. Differences from other results are partly due to the use of quarterly data. In economics, Okun's law is an empirically observed relationship between unemployment and losses in a country's production. It is named after Arthur Melvin Okun, who first proposed the relationship in 1962.Okun, Arthur M. "Potential GNP: Its Measurement and Significance," American Statistical Association, Proceedings of the Business and Economics Statistics Section 1962. Reprinted with slight changes in Arthur M. Okun, The Political Economy of Prosperity (Washington, D.C.: Brookings Institution, 1970) The "gap version" states that for every 1% increase in the unemployment rate, a country's GDP will be roughly an additional 2% lower than its potential GDP. The "difference version"Knotek, 75 describes the relationship between quarterly changes in unemployment and quarterly changes in real GDP. The stability and usefulness of the law has been disputed.Knotek, 93 Imperfect relationship Okun's law may more accurately be called "Okun's rule of thumb" because it is an approximation based on empirical observation rather than a result derived from theory. Okun's law is approximate because factors other than employment, such as productivity, affect output. In Okun's original statement of his law, a 2% increase in output corresponds to a 1% decline in the rate of cyclical unemployment; a 0.5% increase in labor force participation; a 0.5% increase in hours worked per employee; and a 1% increase in output per hours worked (labor productivity).Okun, 1962 Okun's law states that a one-point increase in the cyclical unemployment rate is associated with two percentage points of negative growth in real GDP. The relationship varies depending on the country and time period under consideration. The relationship has been tested by regressing GDP or GNP growth on change in the unemployment rate. Martin Prachowny estimated about a 3% decrease in output for every 1% increase in the unemployment rate. However, he argued that the majority of this change in output is actually due to changes in factors other than unemployment, such as capacity utilization and hours worked. Holding these other factors constant reduces the association between unemployment and GDP to around 0.7% for every 1% change in the unemployment rate. The magnitude of the decrease seems to be declining over time in the United States. According to Andrew Abel and Ben Bernanke, estimates based on data from more recent years give about a 2% decrease in output for every 1% increase in unemployment. There are several reasons why GDP may increase or decrease more rapidly than unemployment decreases or increases: As unemployment increases, * a reduction in the multiplier effect created by the circulation of money from employees * unemployed persons may drop out of the labor force (stop seeking work), after which they are no longer counted in unemployment statistics * employed workers may work shorter hours * labor productivity may decrease, perhaps because employers retain more workers than they need One implication of Okun's law is that an increase in labor productivity or an increase in the size of the labor force can mean that real net output grows without net unemployment rates falling (the phenomenon of "jobless growth") Okun's Law is sometimes confused with Lucas wedge. Mathematical statements The gap version of Okun's law may be written (Abel & Bernanke 2005) as: :\frac{\overline{Y}-Y}{\overline{Y}} = c(u-\overline{u}), where * Y is actual output * \overline{Y} is potential GDP * u is actual unemployment rate * \overline{u} is the natural rate of unemployment * c is the factor relating changes in unemployment to changes in output In the United States since 1955 or so, the value of c has typically been around 2 or 3, as explained above. The gap version of Okun's law, as shown above, is difficult to use in practice because \overline{Y} and \overline{u} can only be estimated, not measured. A more commonly used form of Okun's law, known as the difference or growth rate form of Okun's law, relates changes in output to changes in unemployment: :\frac{\Delta Y}{Y} = k - c \Delta u\,, where: * Y and c are as defined above * \Delta Y is the change in actual output from one year to the next * \Delta u is the change in actual unemployment from one year to the next * k is the average annual growth rate of full-employment output At the present time in the United States, k is about 3% and c is about 2, so the equation may be written :\frac{\Delta Y}{Y} = 0.03 - 2 \Delta u.\, The graph at the top of this article illustrates the growth rate form of Okun's law, measured quarterly rather than annually. Derivation of the growth rate form We start with the first form of Okun's law: :\frac{\overline{Y}-Y}{\overline{Y}} = 1-\frac{Y}{\overline{Y}} = c(u-\overline{u}) :\frac{Y}{\overline{Y}}-1 = c(\overline{u}-u). Taking annual differences on both sides, we obtain :\Delta\left(\frac{Y}{\overline{Y}}\right) = \frac{Y + \Delta Y}{\overline{Y}+ \Delta \overline{Y}} - \frac{Y}{\overline{Y}} = c(\Delta \overline{u}-\Delta u). Putting both numerators over a common denominator, we obtain :\frac{\overline{Y} \Delta Y - Y \Delta \overline{Y}}{\overline{Y}(\overline{Y} + \Delta \overline{Y})}= c(\Delta \overline{u}-\Delta u). Multiplying the left hand side by \frac{\overline{Y} + \Delta \overline{Y}}{Y}, which is approximately equal to 1, we obtain :\frac{\overline{Y} \Delta Y - Y \Delta \overline{Y}}{\overline{Y}Y} = \frac{\Delta Y}{Y} - \frac{\Delta \overline{Y}}{\overline{Y}} \approx c(\Delta \overline{u}-\Delta u) :\frac{\Delta Y}{Y} \approx \frac{\Delta \overline{Y}}{\overline{Y}} + c(\Delta \overline{u}-\Delta u). We assume that \Delta \overline{u}, the change in the natural rate of unemployment, is approximately equal to 0. We also assume that \frac{\Delta \overline{Y}}{\overline{Y}}, the growth rate of full-employment output, is approximately equal to its average value, k. So we finally obtain :\frac{\Delta Y}{Y} \approx k - c \Delta u. Usefulness Through comparisons between actual data and theoretical forecasting, Okun's law proves to be an invaluable tool in predicting trends between unemployment and real GDP. However, the accuracy of the data theoretically proved through Okun's law compared to real world numbers proves to be generally inaccurate. This is due to the variances in Okun's coefficient. Many, including the Reserve Bank of Australia, conclude that information proved by Okun's law to be acceptable to a certain degree. Also, some findings have concluded that Okun's law tends to have higher rates of accuracy for short-run predictions, rather than long-run predictions. Forecasters have concluded this to be true due to unforeseen market conditions that may affect Okun's coefficient. As such, Okun's law is generally acceptable by forecasters as a tool for short-run trend analysis between unemployment and real GDP, rather than being used for long run analysis as well as accurate numerical calculations. The San Francisco Federal Reserve Bank determined through the use of empirical data from past recessions in the 1970s, 1990s, and 2000s that Okun’s law was a useful theory. All recessions showed two common main trends: a counterclockwise loop for both real-time and revised data. The recoveries of the 1990s and 2000s did have smaller and tighter loops.https://www.frbsf.org/economic- research/publications/economic-letter/2014/april/okun-law-deviation- unemployment-recession/ See also * Lucas wedge NotesReferences Abel, Andrew B. & Bernanke, Ben S. (2005). Macroeconomics (5th ed.). Pearson Addison Wesley. . *Baily, Martin Neil & Okun, Arthur M. (1965) The Battle Against Unemployment and Inflation: Problems of the Modern Economy. New York: W.W. Norton & Co.; (1983; 3rd revised edition). *Case, Karl E. & Fair, Ray C. (1999). Principles of Economics (5th ed.). Prentice-Hall. . *Okun, Arthur M. (1962). "Potential GNP, its measurement and significance". Cowles Foundation, Yale University. *Plosser, Charles I. and Schwert, G. William (1979). "Potential GNP: Its measurement and significance: A dissenting opinion", Carnegie-Rochester Conference Series on Public Policy *Knotek, Edward S. "How Useful Is Okun's Law." Economic Review, Federal Reserve Bank of Kansas City, Fourth Quarter 2007, pp. 73–103. *Prachowny, Martin F. J. (1993). "Okun's Law: Theoretical Foundations and Revised Estimates," The Review of Economics and Statistics, 75 (2), pp. 331–336. *Gordon, Robert J., Productivity, Growth, Inflation and Unemployment, Cambridge University Press, 2004 *McBride, Bill (11 October 2010). "Real GDP Growth and the Unemployment Rate". Calculated Risk. Retrieved 5 December 2010. Economics laws Rules of thumb Unemployment 1962 in economics Gross domestic product "

❤️ Emergency brake (train) 🦚

"class 317 electric multiple unitalt=British electric train driver's brake On trains, the expression emergency brake has several meanings: * The maximum brake force available to the engine driver from the conventional braking system, usually operated by taking the brake handle to its furthest position, through a gate mechanism, or by pushing a separate plunger in the cab. * A completely separate mechanism from the conventional braking system, designed to stop the train as quickly as possible. * A handle or plunger which may be applied by a passenger in an emergency situation, either stopping the train directly or sending an alarm to the driver so that they can stop the train. The emergency brake applies considerably more braking force than the standard full-service brake. The engine driver or motorman will only use the emergency brake as a last resort, since it may cause damage; even with modern wheel slide protection, a train may develop wheel-flats, and the rails themselves can suffer profile damage. Possible consequences of operation Putting the engine driver's brake handle into the emergency position may also: * Shut off traction power * On an electric train, drop the pantograph if the power supply is overhead-wire traction current, or raise the pickup shoes where the supply is third rail traction current * Disable dynamic braking * Prevent the brakes from being released until the train has stopped * Connect the brake wires to ground, to prevent a "false-feed" voltage from releasing the brakes * Send an emergency radio signal, if the brake handle has been in the emergency position for over 30 seconds *Activate the sander *Activate the train horn until the selector is placed out of the emergency position Passenger-applied brakes Trains often have a facility in each car to enable passengers to apply the brakes in case of emergency. In many modern trains, the driver is able to prevent brake activation when a passenger operates the emergency alarmSoutheastern Traction Manual - Class 465/6: Passenger Communication Equipment \- an audible warning is sounded, and the driver is then able to talk to the person who activated the alarm on the intercom and see them on an internal CCTV. The driver can press an override button and hold the brakes off whilst they choose a safe place to stop the train. Because of possible serious problems, severe fines and/or imprisonment penalties are in place to deter people from activating the brake without good reason. =Mechanism on locomotive-hauled stock with brake pipe= The alarm chain in a passenger coach is designed to create a break in the continuity of the brake pipes (whether vacuum or air brakes), immediately resulting in a loss of brake pressure (or vacuum) and thereby causing the train brakes to be applied. With vacuum brakes, a clappet valve is provided, which is released by the pulling of the alarm chain; with air brakes, there is a similar passenger emergency valve which can vent the brake pipe to the air. In most locomotives (in addition to a warning lamp or buzzer being sounded) the master controller undergoes auto-regression, with the notches falling to zero rapidly as the locomotive's motive power is switched off. The guard may also notice the loss of brake pressure (although they may not know it is due to the pulling of the alarm chain) and is expected to apply their brakes immediately as well. It is possible for a driver to override the alarm-chain pull; this is sometimes done where it is known that miscreants resort to pulling the emergency chain solely to get the train to stop at a point convenient for themselves. However, such an act by the driver (or guard) of deliberately ignoring an indication of alarm-chain pulling is a serious matter. In recent years locomotives have been fitted with emergency flashers on the roof of the cab, and these flashers are also activated when the brake pipe pressure is lost for any reason other than the driver's application of the brake valve. This alerts drivers of oncoming trains of the possibility of a derailed or parted rake which may foul other tracks (since brake pressure may have been lost for those reasons as well); at the locomotive, it is not possible to tell whether the loss of brake pressure is due to the pulling of the alarm chain. ACP (alarm chain pulling) also causes a small lever to be released near the emergency brake valve (usually mounted near one end of the coach), which does not retract to its normal position even when the chain is released. This allows the driver (or guard) to find out in which coach the ACP actually occurred. When the coach is isolated, the lever needs to be manually reset. Until this is done, the lamp and buzzer in the locomotive cab are continuously activated. A circuit breaker controls the lamp and alarm bell in the locomotive cab; in cases where defective equipment causes the lamp and bell to go off, the driver can disable them by placing the MCB (miniature circuit breaker) in the "Off" position. Despite the obvious safety hazards, sometimes this is resorted to by drivers when driving trains through sections where spurious ACP incidents are very common. Around the world=Germany= The Regelung B009 NBÜ Rev 3.1 defines a set of nested statemachines in the chapter “Anlage 1: Phasen einer Zugfahrt“, reflecting a very wide range of usecases, including platforms, tunnels, etc. and is applicable for subways, trams, metros(S-Bahn), as it implements appropriate actions for all usecases occurring in rail transportation. These statemachines represents the state of the art in Germany, it is highly recommended to be implemented or retrofitted to avoid the problems experienced at the S-Bahn Rhine-Neckar. In Germany, passenger vehicles “must have easily visible and reachable emergency brake handles”.§ 23 paragraph 3 sentence 1 EBO It is allowed that the emergency brake can be reset,§ 23 paragraph 3 sentence 2 EBO on S-Bahn vehicles (i.e. Classes 420, 423, 425, 480 or 481) it's allowed to only result in a display when used outside of platforms. The implementation of the S-Bahn's emergency brake however does currently not reflect the state of the art in Germany, it has failed in practical use at least in one instance 2015, as a driver lost consciousness completely, but still accidentally triggered the vigilance device. Unlike the System NBÜ2004, which is used in conventional trains, the brake was not activated, because it is only an indicator light and a sound, while the train is running on the track. Without ATP enabled or over-speed, the described incident may have been leading to fatalities and substantial damage, as the passengers noticed the unconscious driver, but could not stop the train by pulling the emergency-brake-handle. Using the NBÜ2004, as used in regional- and long-distance-trains, this would have been prevented, a "overwrite" response is needed, typically the "FÜ"(Filling) position of the automatic brake-lever, otherwise the trains brake-computer will perform an emergency-brake after 10 seconds. Equipment for this override (NBÜ) is necessary in tunnels above 1000 m. For regional trains, UIC 541-5 is not sufficient since 2011, long distance trains must at least be equipped with UIC 541-5.EBA-Tunnelrichtlinie chapter 3.2 (long and very long tunnels being defined in chapter 1.2) The sections where not to stop are marked with yellow bars on the kilometer signs. Regional trains, except MUs, are usually equipped with NBÜ 2004, which results in a display and a break a few seconds later if the train driver doesn't respond. For DB Regio, the rules for the staff are given in Ril 494. Long distance trains are mostly equipped with system DB, which uses the UIC 558 control wire, which results in conflicts with some door control systems and is therefore not used in regional trains. In MUs, usually a special implementation is used. For trams, emergency brakes are also necessary.§ 36 paragraph 9 sentence 1 BOStrab In tunnels and track sections without safety area, using them outside a station may stop the tram at the next platform instead of immediately.§ 36 paragraph 9 sentence 2 BOStrab =India= Emergency brake on a train in alt=Emergency brake with red handle Chain-pulling is the act of pulling a cord that activates the train's emergency brakes to stop a train, whether for a genuine emergency or (often) illegally for someone to get on or off the train on the Indian Railway network. Illegal chain-pulling is a serious problem on Indian railways; where miscreants do so to make unscheduled stops near their destination, which delays trains. Penalties for misuse of this facility include a fine of Rs. 1,000 and/or imprisonment up to one year. In an effort to improve the service, former President of India Dr. A. P. J. Abdul Kalam proposed an alternate method wherein a passenger in an emergency communicates with the guard and driver of the train. =United States= Bombardier commuter rail equipment, Sounder, Seattle, WA In the USA, an emergency stop cord is not used. Any visible cord running within the body of a railway car would have been what was known as the "communicating cord". This was a method of signalling the engine operator (known in the US as the "engineer"). Unlike other countries, it was never intended for use by passengers. It had its own code of signals, similar to engine whistle signals. Drivers receiving an unusual, or unidentifiable, communicating signal might stop the train, perhaps as a "normal stop" or an "emergency application", at their discretion. A long, continuous signal would usually prompt a driver to make an emergency stop. Emergency brake valves are always located on the bulkheads, inside the body of the car next to its end doors. The emergency brake valve is covered by a metal or clear plastic shield labelled "Emergency Only". Sometimes there was also a communicating signal handle on the inside bulkhead, labelled "signal". Mistakenly identifying the communication cord as the emergency brake can lead to confusion about how emergency braking works on US trains. Once an emergency brake valve is opened, all of the air in the braking system, except those of the locomotive(s), which are equipped with brakes controlled separately (independent brake) from those of the cars, is evacuated, immediately placing the train cars' brakes into emergency, just as if there had been an uncoupling of cars (a "separation"). All available pressure from the Equalizing Reservoir will go into the Brake Pipe, thus running the length of the train, actuating the train brakes on each car. No action is required (or even possible) on the part of the engineer. The train will stop, no matter what they do. There is no override. Once the train has stopped, the braking system will not recharge (pressurize) until the emergency valve has been closed. This means a member of the train crew must locate the open valve, and ascertain that there is no problem which would make it unsafe to release the brakes and proceed. Identification of the valve is possible by the sound of air escaping from it. In many cars (and practically all cars built post-WWII), the communicating cord was only located in the vestibule, unless the car was of such a type that it did not have a vestibule, such as a dining or lounge car. In newer Amtrak equipment, the air-operated communicating system was electrified, and operated by pressing a button located in the vestibule. The old communicating systems have been gradually supplanted by radios, although they were still required on US passenger equipment until relatively recently. The emergency brake valve continues to be located on the inside bulkhead, or in a consistent (standard) location specified by safety regulations. A member of the train crew must walk the length of the train and inspect it for any damage. The consist will need to be inspected before it can return to normal revenue service. In the cabs of light-rail cars the emergency brake is often a large red button, which the train crew refers to as the "mushroom"; this also activates the magnetic track brakes. The mechanism of an emergency brake may differ, depending on railcar design. Emergency-braking a train (without track brakes) will give about 1.5 m/s2 (0.15 g) deceleration. The braking distance will be approximately at and at . High-speed trains are usually equipped with a magnetic track brake, which can give about 0.3 m/s2 extra, and give braking distances of about at and at . = United Kingdom = Emergency brakes were introduced in the United Kingdom by the Regulation of Railways Act 1868. Section 22 stated, "All trains traveling a distance of more than 20 miles without stopping are to be provided with a means of communication between the passengers and the servants of the company in charge of the train". At first, this means of communication was a cord running down the length of the train at roof level outside the carriages, connected to a bell on the locomotive. When the use of automatic brakes was made compulsory in the Regulation of Railways Act 1889, the equipment was modified so that it operated the brakes; however, the term "communication cord" has survived. Until the 1970s a "cord" (by that time a chain) was still used, which ran the length of the carriage and connected to a valve at one end which opened the brake pipe. The exposed section of chain was painted red, with the coiled section behind the wall painted black. The system was designed so that as the black length of chain was exposed, it would not retract so as to identify which particular chain in that carriage was pulled. A butterfly valve on the side of the carriage was used to reset the brake, and also made it easy for the train crew to see in which coach the cord had been pulled. Later designs used handles which were activated by pulling down; more recent types use buttons connected to a PassComm system. On modern trains with sliding doors the body-indicator light (BIL), usually used to show that doors on a carriage are open, will flash when the brake has been used. Pulling the alarm chain on a British train will pull a lever connected to the brake pipe flaps. Pulling the alarm activates a piston, causing the flaps to be opened and all the air pushed out the air tube, forcing the brakes on. In the driver's cab, a buzzer and a light will tell that the alarm has been activated. In the guard's van, this is seen from a valve which shows loss of pressure in the brake pipe. In the UK, there is a fine (of level 3 on the standard scale: up to £1000 as of 2018) for pulling the alarm chain without reasonable cause.Railways Byelaws made in 2005, s.11(3) Override In most rolling stock built since the 1980s, passenger communication handles (or PassComms) have been installed, which activate an alarm in the driver's cab when used. If the train is not in a safe place (in a tunnel or on a bridge, for example) the driver has approximately three seconds to override the alarm by pressing a button before the brakes automatically apply. The driver may also speak to the person who pulled the handle via an intercom mounted alongside the handle. On modern trains this is particularly useful, since the PassComm must be much easier to use and more accessible due to accessibility regulations. However this also makes accidental activation easier. On some modern trains, the PassComm in a disabled-friendly toilet is mounted such that it is often confused with the door or flush control; this sometimes leads to accidental activation. As a result, on some models of train such as the Class 180, the alarm panels fitted in the toilets do not operate the train brake, and simply alert the train crew to the emergency. London Underground When London Underground began converting trains for one-person-operation during the 1970s and 1980s, the original emergency brake systems were replaced by an alarm and a passenger-communication system. On earlier systems the brakes were not applied automatically (being under the control of the driver), whereas later systems have an override as above. On older systems, marker boards showing an exclamation mark were provided on departure from each station at the point where the rear of the train would no longer be at the platform. Normally, if the alarm was activated before the board the driver would stop the train, and otherwise continue to the next station. These boards were replaced by a number of boards counting up the number of cars that are beyond the end of the platform; for example, on a line with six-car trains the boards show 1, 2, 3, 4, 5, 6. When a train has stopped, they help the driver to see how much of the train is at the platform. With the help of passenger communication and available station staff, the driver can then decide whether to deal with the situation as it is, continue to the next station or possibly reverse back into the station (after consulting with line controllers and proper safety measures). During hot summer weather passengers are warned against using the emergency alarms if feeling unwell, since it can delay trains and increase the problem; they are instead instructed to leave the train at the next station and get some fresh air or a cold drink. = Russia = In Russian trains there is usually an emergency brake known as a "stop valve" (). In elektrichkas and other trains it is usually located near the doors, and sometimes in the middle of the coach as well. A stop valve usually has a distinctive red handle. Turning the handle down (anti-clockwise) by about 90 degrees causes pneumatic brakes to engage, due to pressure loss in the standard air-braking system. While primitive and not allowing any override such a system is effective, resembling usual train brake activation; it does not fail in emergency conditions. More complicated systems may not provide quick braking when needed, or during a communications failure. Emergency braking is somewhat risky; it is hard on passengers, and there is a risk of passenger injury if braking occurs at high speed. As a result, use of a stop valve without good reason is prohibited and may lead to fines. Depending on circumstances and consequences, authorities may even arrest a person for the incorrect use of a stop valve. Subways In subways, derailment is usually less dangerous (speeds are lower, trains cannot jackknife in tunnels and so on). It is dangerous to stop in a tunnel if a fire develops; an emergency exit could lead to electrocution by the third rail (typically energized with 825 volts DC). Instead drivers try to reach the next station, even in an emergency. As a result, there are no emergency brakes directly visible to passengers. However, there are hidden stop valves and simplified train controls, allowing each coach to act on its own in need. In an emergency, there are door-control handles (visible to passengers) which are intended to make the pneumatic train doors able to be opened by removing air pressure. Subway trains have mechanisms and alarms which prevent trains from moving if the doors are open, and alert the driver or engage the brakes if doors open while a train is moving. Penalties for misuse of emergency door- opening handles are similar to those for stop-valve misuse. =Japan= An EB reset switch in a JR West 221 series EMU In many Japanese passenger and freight trains, an EB reset switch is provided which is activated by sounding a buzzer and lighting up the EB reset switch when the driver does not operate the controls within 60 seconds of last operation (30 seconds on Aonami Line, 40 seconds on JR Kyushu lines). If the EB switch is not pressed (reset) within 5 seconds of being activated, it will trigger an emergency brake application so as to prevent accidents due to driver error or when the driver is incapacitated. Also, a red button and/or an emergency brake setting on the levers are provided in the driver's cab so the driver can manually activate the emergency brake; these can also be activated (like a dead man's handle) when the driver feels unwell or is incapacitated in trains without the EB reset switch. Near train doors, emergency brake cords are available so that passengers can bring the train to a halt in an emergency. External signalling In the US, the universally recognized signal to stop is a sweeping, horizontal hand motion, back-and-forth, at arm's length and perpendicular to the track (preferably in a downward direction, so as to distinguish it from a mere greeting). This can be done with an object (such as a light or flag) or an empty hand. In US railroad slang it is referred to as a "washout", or "washing out" signal, or a "signing down", and requires an immediate stop. If the driver's vision is limited, or they feel it necessary, they will make an emergency stop. Drivers are trained to interpret any urgent waving or signalling by a person near the track as a possible warning of danger, perhaps requiring an immediate stop, depending upon the particular circumstances present. Images {Mass Rapid Transit emergency plunger in Singapore activated from the station platform. The penalty for misuse is S$5,000alt=Emergency brake button on Singapore train alt=British train alarm, near car ceiling alt=Old German pull-handle emergency brake } Further reading * See also * Air brake (rail) * Air brake (road vehicle) * Counterweight brake * Dead-man's brake * Dead-man's vigilance device * Hand brake * Hydraulic brake * Pulled tail References Railway brakes Train protection systems "

❤️ Survival of the fittest 🦚

"Herbert Spencer coined the phrase "survival of the fittest". "Survival of the fittest" is a phrase that originated from Darwinian evolutionary theory as a way of describing the mechanism of natural selection. The biological concept of fitness is defined as reproductive success. In Darwinian terms the phrase is best understood as "Survival of the form that will leave the most copies of itself in successive generations." Herbert Spencer first used the phrase, after reading Charles Darwin's On the Origin of Species, in his Principles of Biology (1864), in which he drew parallels between his own economic theories and Darwin's biological ones: "This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called 'natural selection', or the preservation of favoured races in the struggle for life." ^ "Herbert Spencer in his Principles of Biology of 1864, vol. 1, p. 444, wrote: 'This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called "natural selection", or the preservation of favoured races in the struggle for life.'" , citing HERBERT SPENCER, THE PRINCIPLES OF BIOLOGY 444 (Univ. Press of the Pac. 2002.) Darwin responded positively to Alfred Russel Wallace's suggestion of using Spencer's new phrase "survival of the fittest" as an alternative to "natural selection", and adopted the phrase in The Variation of Animals and Plants under Domestication published in 1868."This preservation, during the battle for life, of varieties which possess any advantage in structure, constitution, or instinct, I have called Natural Selection; and Mr. Herbert Spencer has well expressed the same idea by the Survival of the Fittest. The term "natural selection" is in some respects a bad one, as it seems to imply conscious choice; but this will be disregarded after a little familiarity." In On the Origin of Species, he introduced the phrase in the fifth edition published in 1869,"This preservation of favourable variations, and the destruction of injurious variations, I call Natural Selection, or the Survival of the Fittest." – intending it to mean "better designed for an immediate, local environment"."Evolutionary biologists customarily employ the metaphor 'survival of the fittest,' which has a precise meaning in the context of mathematical population genetics, as a shorthand expression when describing evolutionary processes." History of the phrase By his own account, Herbert Spencer described a concept similar to "survival of the fittest" in his 1852 "A Theory of Population". He first used the phrase – after reading Charles Darwin's On the Origin of Species – in his Principles of Biology of 1864Vol. 1, p. 444 in which he drew parallels between his economic theories and Darwin's biological, evolutionary ones, writing, "This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called 'natural selection', or the preservation of favored races in the struggle for life." In July 1866 Alfred Russel Wallace wrote to Darwin about readers thinking that the phrase "natural selection" personified nature as "selecting", and said this misconception could be avoided "by adopting Spencer's term" Survival of the fittest. Darwin promptly replied that Wallace's letter was "as clear as daylight. I fully agree with all that you say on the advantages of H. Spencer's excellent expression of 'the survival of the fittest'. This however had not occurred to me till reading your letter. It is, however, a great objection to this term that it cannot be used as a substantive governing a verb". Had he received the letter two months earlier, he would have worked the phrase into the fourth edition of the Origin which was then being printed, and he would use it in his "next book on Domestic Animals etc.". Darwin wrote on page 6 of The Variation of Animals and Plants under Domestication published in 1868, "This preservation, during the battle for life, of varieties which possess any advantage in structure, constitution, or instinct, I have called Natural Selection; and Mr. Herbert Spencer has well expressed the same idea by the Survival of the Fittest. The term "natural selection" is in some respects a bad one, as it seems to imply conscious choice; but this will be disregarded after a little familiarity". He defended his analogy as similar to language used in chemistry, and to astronomers depicting the "attraction of gravity as ruling the movements of the planets", or the way in which "agriculturists speak of man making domestic races by his power of selection". He had "often personified the word Nature; for I have found it difficult to avoid this ambiguity; but I mean by nature only the aggregate action and product of many natural laws,—and by laws only the ascertained sequence of events." In the first four editions of On the Origin of Species, Darwin had used the phrase "natural selection". In Chapter 4 of the 5th edition of The Origin published in 1869, Darwin implies again the synonym: "Natural Selection, or the Survival of the Fittest". By "fittest" Darwin meant "better adapted for the immediate, local environment", not the common modern meaning of "in the best physical shape" (think of a puzzle piece, not an athlete). In the introduction he gave full credit to Spencer, writing "I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection, in order to mark its relation to man's power of selection. But the expression often used by Mr. Herbert Spencer of the Survival of the Fittest is more accurate, and is sometimes equally convenient." In The Man Versus The State, Spencer used the phrase in a postscript to justify a plausible explanation of how his theories would not be adopted by "societies of militant type". He uses the term in the context of societies at war, and the form of his reference suggests that he is applying a general principle.The principle of natural selection applied to groups of individual is known as Group selection. > "Thus by survival of the fittest, the militant type of society becomes > characterized by profound confidence in the governing power, joined with a > loyalty causing submission to it in all matters whatever". (snippet) Though Spencer's conception of organic evolution is commonly interpreted as a form of Lamarckism, Herbert Spencer is sometimes credited with inaugurating Social Darwinism. The phrase "survival of the fittest" has become widely used in popular literature as a catchphrase for any topic related or analogous to evolution and natural selection. It has thus been applied to principles of unrestrained competition, and it has been used extensively by both proponents and opponents of Social Darwinism. Evolutionary biologists criticise the manner in which the term is used by non-scientists and the connotations that have grown around the term in popular culture. The phrase also does not help in conveying the complex nature of natural selection, so modern biologists prefer and almost exclusively use the term natural selection. The biological concept of fitness refers to reproductive success, as opposed to survival, and is not explicit in the specific ways in which organisms can be more "fit" (increase reproductive success) as having phenotypic characteristics that enhance survival and reproduction (which was the meaning that Spencer had in mind). Critiquing the phrase While the phrase "survival of the fittest" is often used to mean "natural selection", it is avoided by modern biologists, because the phrase can be misleading. For example, survival is only one aspect of selection, and not always the most important. Another problem is that the word "fit" is frequently confused with a state of physical fitness. In the evolutionary meaning "fitness" is the rate of reproductive output among a class of genetic variants. Interpreted as expressing a biological theory The phrase can also be interpreted to express a theory or hypothesis: that "fit" as opposed to "unfit" individuals or species, in some sense of "fit", will survive some test. Nevertheless, when extended to individuals it is a conceptual mistake, the phrase is a reference to the transgenerational survival of the heritable attributes; particular individuals are quite irrelevant. This becomes more clear when referring to Viral quasispecies, in survival of the flattest, which makes it clear to survive makes no reference to the question of even being alive itself; rather the functional capacity of proteins to carry out work. Interpretations of the phrase as expressing a theory are in danger of being tautological, meaning roughly "those with a propensity to survive have a propensity to survive"; to have content the theory must use a concept of fitness that is independent of that of survival."Stephen Jay Gould, Darwin's Untimely Burial", 1976; from Philosophy of Biology:An Anthology, Alex Rosenberg, Robert Arp ed., John Wiley & Sons, May 2009, pp. 99–102.von Sydow, M. (2014). ‘Survival of the Fittest’ in Darwinian Metaphysics – Tautology or Testable Theory? (pp. 199–222) In E. Voigts, B. Schaff & M. Pietrzak-Franger (Eds.). Reflecting on Darwin. Farnham, London: Ashgate. Interpreted as a theory of species survival, the theory that the fittest species survive is undermined by evidence that while direct competition is observed between individuals, populations and species, there is little evidence that competition has been the driving force in the evolution of large groups such as, for example, amphibians, reptiles, and mammals. Instead, these groups have evolved by expanding into empty ecological niches. In the punctuated equilibrium model of environmental and biological change, the factor determining survival is often not superiority over another in competition but ability to survive dramatic changes in environmental conditions, such as after a meteor impact energetic enough to greatly change the environment globally. The main land dwelling animals to survive the K-Pg impact 66 million years ago had the ability to live in tunnels, for example. In 2010 Sahney et al. argued that there is little evidence that intrinsic, biological factors such as competition have been the driving force in the evolution of large groups. Instead, they cited extrinsic, abiotic factors such as expansion as the driving factor on a large evolutionary scale. The rise of dominant groups such as amphibians, reptiles, mammals and birds occurred by opportunistic expansion into empty ecological niches and the extinction of groups happened due to large shifts in the abiotic environment. Interpreted as expressing a moral theory=Social Darwinists= It has been claimed that "the survival of the fittest" theory in biology was interpreted by late 19th century capitalists as "an ethical precept that sanctioned cut-throat economic competition" and led to the advent of the theory of "social Darwinism" which was used to justify laissez-faire economics, war and racism. However, these ideas predate and commonly contradict Darwin's ideas, and indeed their proponents rarely invoked Darwin in support. The term "social Darwinism" referring to capitalist ideologies was introduced as a term of abuse by Richard Hofstadter's Social Darwinism in American Thought published in 1944. =Anarchists= Russian anarchist Peter Kropotkin viewed the concept of "survival of the fittest" as supporting co-operation rather than competition. In his book Mutual Aid: A Factor of Evolution he set out his analysis leading to the conclusion that the fittest was not necessarily the best at competing individually, but often the community made up of those best at working together. He concluded that > In the animal world we have seen that the vast majority of species live in > societies, and that they find in association the best arms for the struggle > for life: understood, of course, in its wide Darwinian sense – not as a > struggle for the sheer means of existence, but as a struggle against all > natural conditions unfavourable to the species. The animal species, in which > individual struggle has been reduced to its narrowest limits, and the > practice of mutual aid has attained the greatest development, are invariably > the most numerous, the most prosperous, and the most open to further > progress. Applying this concept to human society, Kropotkin presented mutual aid as one of the dominant factors of evolution, the other being self-assertion, and concluded that > In the practice of mutual aid, which we can retrace to the earliest > beginnings of evolution, we thus find the positive and undoubted origin of > our ethical conceptions; and we can affirm that in the ethical progress of > man, mutual support not mutual struggle – has had the leading part. In its > wide extension, even at the present time, we also see the best guarantee of > a still loftier evolution of our race. Tautology "Survival of the fittest" is sometimes claimed to be a tautology. The reasoning is that if one takes the term "fit" to mean "endowed with phenotypic characteristics which improve chances of survival and reproduction" (which is roughly how Spencer understood it), then "survival of the fittest" can simply be rewritten as "survival of those who are better equipped for surviving". Furthermore, the expression does become a tautology if one uses the most widely accepted definition of "fitness" in modern biology, namely reproductive success itself (rather than any set of characters conducive to this reproductive success). This reasoning is sometimes used to claim that Darwin's entire theory of evolution by natural selection is fundamentally tautological, and therefore devoid of any explanatory power. However, the expression "survival of the fittest" (taken on its own and out of context) gives a very incomplete account of the mechanism of natural selection. The reason is that it does not mention a key requirement for natural selection, namely the requirement of heritability. It is true that the phrase "survival of the fittest", in and by itself, is a tautology if fitness is defined by survival and reproduction. Natural selection is the portion of variation in reproductive success that is caused by heritable characters (see the article on natural selection). If certain heritable characters increase or decrease the chances of survival and reproduction of their bearers, then it follows mechanically (by definition of "heritable") that those characters that improve survival and reproduction will increase in frequency over generations. This is precisely what is called "evolution by natural selection". On the other hand, if the characters which lead to differential reproductive success are not heritable, then no meaningful evolution will occur, "survival of the fittest" or not: if improvement in reproductive success is caused by traits that are not heritable, then there is no reason why these traits should increase in frequency over generations. In other words, natural selection does not simply state that "survivors survive" or "reproducers reproduce"; rather, it states that "survivors survive, reproduce and therefore propagate any heritable characters which have affected their survival and reproductive success". This statement is not tautological: it hinges on the testable hypothesis that such fitness-impacting heritable variations actually exist (a hypothesis that has been amply confirmed.) Momme von Sydow suggested further definitions of 'survival of the fittest' that may yield a testable meaning in biology and also in other areas where Darwinian processes have been influential. However, much care would be needed to disentangle tautological from testable aspects. Moreover, an "implicit shifting between a testable and an untestable interpretation can be an illicit tactic to immunize natural selection ... while conveying the impression that one is concerned with testable hypotheses".Cf. von Sydow, M. (2012). From Darwinian Metaphysics towards Understanding the Evolution of Evolutionary Mechanisms: A Historical and Philosophical Analysis of Gene-Darwinism and Universal Darwinism. Universitätsverlag Göttingen. Skeptic Society founder and Skeptic magazine publisher Michael Shermer addresses the tautology problem in his 1997 book, Why People Believe Weird Things, in which he points out that although tautologies are sometimes the beginning of science, they are never the end, and that scientific principles like natural selection are testable and falsifiable by virtue of their predictive power. Shermer points out, as an example, that population genetics accurately demonstrate when natural selection will and will not effect change on a population. Shermer hypothesizes that if hominid fossils were found in the same geological strata as trilobites, it would be evidence against natural selection.Shermer, Michael; Why People Believe Weird Things; 1997; Pages 143–144 See also Red Queen hypothesis NotesReferencesExternal links=Origins of the phrase= * AboutDarwin.com — Darwin's Timeline * Pioneers of Psychology * Evolution Quotations compiled by GIGA =Tautology links= * Darwin's Untimely Burial by Stephen Jay Gould * Evolution and Philosophy: A Good Tautology is Hard to Find by John Wilkins, part of the talk.origins archive. * CA500: "Survival of the fittest is a tautology" from the talk.origins index to creationist claims by Mark Ridley. * Is "survival of the fittest" a tautology by Don Lindsay. * Darwin's Great Tautology by the Doubting Thomas =Morality link= * CA002: Survival of the fittest implies that "might makes right" * David Hume — Dialogues Concerning Natural Religion * Evolution and philosophy — Does evolution make might right? by John S. Wilkins. =Kropotkin: Mutual Aid= Mutual Aid: A Factor of Evolution – HTML version at the Anarchy Archives Charles Darwin Herbert Spencer Biological evolution English phrases Metaphors ta:தக்கன பிழைக்கும் "