All Quotes

"[T]hey share the traits of the acute successful randomness fool who, in addition, operates in the most random of environments. ...[T]heir bosses and employers shared the same trait. They, too, are permanently out of the market."

"There is a saying that bad traders divorce their spouse sooner than abandon their positions. Loyalty to ideas is not a good thing for traders, scientists - or anyone."

"Consider that the turkey's experience may have, rather than no value, a negative value. It learned from observation, as we are all advised to do (hey, after all, this is what is believed to be the scientific method). Its confidence increased as the number of friendly feedings grew, and it felt increasingly safe even though the slaughter was more and more imminent. Consider that the feeling of safety reached its maximum when the risk was at the highest!"

"Just as an animal could have survived because its sample path was lucky... free of the evolutionary rare event, the "best" operators in a given business can... One vicious attribute is that the longer these... can go without encountering the rare event, the more vulnerable they will be to it. ...[S]hould one extend time to infinity, then by , that event will happen with certainty—the species will be wiped out! For evolution means fitness to... only one time series, not the average of all possible environments."

"Why do [people] confuse probability and expectation, that is, probability [vs.] probability times payoff? Mainly because much... schooling comes from examples in symmetric environments... the... bell curve... is entirely symmetric."

"I have organized my career and business in such a way as to... benefit... I am profiting from the rare event, with asymmetric bets."

"In most disciplines... asymmetry does not matter. ...People in most fields ...do not have problems eliminating extreme values from their sample, when the difference in payoff between different outcomes is not significant ...A professor ...removes the ...s, and takes the average of the remaining ones, without ...being ...unsound. A casual weather forecaster does the same ...So people in finance borrow the technique and ignore infrequent events, not knowing that the effect ...can bankrupt a company."

"Many scientists... are... subject to such foolishness... One flagrant example is... global warming... These scientists initially ignored the fact that these [high temperature] spikes, although rare, had the effect of adding disproportionately to the cumulative melting of the ice caps. ...[A]n event, although rare, that brings large consequences cannot be ignored."

"Sometimes market data becomes a simple trap; it shows you the opposite of its nature... [e.g.,] Currencies that exhibit the largest historical stability... are the most prone to crashes."

"I reject a sole time series of the past as an indication of future performance; I need a lot more than data."

"[W]e read too much into shallow recent history... but not from history in general [which] teaches us that things that never happened before do happen. ...outside of the narrowly defined time series; the broader the look, the better the lesson."

"[T]here is a category of traders who have inverse rare events, for whom volatility is often the bearer of good news. Those traders lose money frequently, but in small amounts, and make money rarely, but in large amounts. ...crisis hunters. I am happy to be one of them."

"Statistics... is all based on... the steady augmentation of the confidence level... [F]or an n times increase in sample size, we increase our knowledge by the square root on n. ...Where statistics ...fails us, is when we have distributions that are not symmetric... If there is a very small probability of finding a red ball in an urn dominated by black ones, then our knowledge about the absence of red balls will increase [even more] slowly. ...On the other hand, our knowledge of the presence of red balls will dramatically improve once one of them is found. This asymmetry in knowledge... is the central philosophical problem for... David Hume and Karl Popper."

"David Hume posed the issue in the following way (as rephrased in the black swan problem by... John Stuart Mill) No amount of observations of white swans can allow the inference that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion."

"Science had shifted, thanks to Bacon, into an emphasis on empirical observation. The problem is that, without a proper method, empirical observations can lead you astray. Hume came to... stress the need for some rigor in the gathering and interpretation of knowledge... epistemology... Hume is the first modern epistemologist... he was an obsessive skeptic and never believed... that a link between two items could be established as being causal."

"Maximizing the probability of winning does not lead to maximizing the expectation from the game when one's strategy may include , i.e., a small chance of a large loss and a large chance of a small win. If you engaged in a Russian Roulette-type strategy... you are likely to show up as the winner in almost all samples—except in the year when you are dead."

"[W]e like to emit logical and rational ideas but we do not enjoy this execution."

"What is easier to remember, a collection of facts glued together, or a story, something that offers a series of logical links? Causality is easier to commit to memory. ...What is induction exactly? ...It is very handy, as the general takes much less room in onel's memory than a collection of particulars. The effect of such compression is the reduction in the degree of detected randomness."

"I will use statistics and inductive methods to make aggressive bets, but I will not use them to manage my risks and exposure. ...[A]ll the surviving traders I know seem to have done the same. ...[T]hey make sure the cost of being wrong is limited ...they know ...which events would prove their conjecture wrong and allow for it ...They would then terminate their trade. This is called a stop loss ...I find it rarely practiced."

"A mistake is not something to be determined after the fact, but in the light of the information until that point."

"I always remind myself that what one observes is at best a combination of variance and returns, not just returns."

"I try to make money infrequently, as infrequently as possible simply because I believe that rare events are not fairly valued, and that the rarer the event, the more undervalued it will be in price."

"The major problem with inference... is that those whose profession it is to derive conclusions from data often fall into the trap faster and more confidently... The more data we have, the more likely we are to drown in it. For common wisdom... is to base... decision making on the following principle: It is very unlikely for someone to perform... well in a consistent fashion without doing something right. ...[I]f someone performed better... in the past then there is a great[er] chance of performing better than the crowd in the future... But... [a] small knowledge of probability can lead to worse results than no knowledge at all."

"[B]ecoming more rational, or not feeling the emotions of social slights, is not part of the human race... not with our current biology. There is no solace to be found from reasoning..."

"Optimism, it is said, is predictive of success. ...It can also be predictive of failure. Optimistic people... take more risks as they are overconfident of the about the odds; those who win show up among the rich and famous, others fail and disappear from the analysis."

"Let us use 10,000 fictional investment managers... [O]nce a manager has a single bad year, he is thrown out of the sample. ...[T]oss a coin; heads and the manager will make $10,000 over the year, tails and he will lose $10,000. ...We have, in a fair game, 313 managers who made money five years in a row. ...[I]f we throw one of these ...into the real world we would get ...comments on his remarkable style, his incisive mind... His biographer will dwell on ...a great mind in the making. ...[S]hould he stop performing (...his odds ...have stayed at 50%) they would start ...finding fault with his dissipated lifestyle. They will find something he stopped doing, and attribute his failure... The truth ...he simply ran out of luck."

"The information that a person derived some profit in the past... by itself, is neither meaningful nor relevant. We need to know the size of the population from which he came. If the initial population is 10,000 managers, I would ignore the results."

"Professor Karl Pearson... devised the first test of nonrandomness... He examined millions of runs of what was called a Monte Carlo (the old name for a roulette wheel)... He discovered... the runs were not purely random. ...Philosophers of statistics call this the reference case problem to explain that there is no true attainable randomness in practice, only in theory."

"Even the fathers of statistical science forgot that a random series is bound to exhibit some pattern... Pearson was among the first scholars interested in creating artificial random number generators, tables one could use as inputs for... simulations (precursors of our Monte Carlo simulator). ...[T]hey did not want these tables to exhibit... regularity. Yet real randomness does not look random! ...A single random run is bound to exhibit some pattern ..."

"At no point during his ordeal did Nero think of himself as 72% alive and 28% dead."

"Probability is not about the odds, but about the belief in the existence of an alternative outcome, cause, or motive."

"We favor the visible, the embedded, the personal, the narrated, and the tangible; we scorn the abstract."

"Wittgenstein's ruler: "Unless you have confidence in the ruler's reliability, if you use a ruler to measure a table you may also be using the table to measure the ruler." (page 224)"

"[E]conomists are evaluated on how intelligent they sound, not on a scientific measure of their knowledge of reality. (page 85)"

"[E]conomics is a narrative discipline, and explanations are easy to fit retrospectively. (page 257)"

"[In] economics... you can disguise charlatanism under the weight of equations and nobody can catch you since there is no such thing as a controlled experiment. Now the spirit of such methods, called scientism by its detractors, continued into the discipline of finance as a few technicians thought their mathematical knowledge could lead them to understand markets. The practice of financial engineering came along with massive doses of pseudoscience. (page 115)"

"I disagree with the followers of Marx and those of Adam Smith: the reason free markets work is because they allow people to be lucky, thanks to aggressive trial and error, not by giving rewards or "incentives" for skill."

"If you want to get an idea of a friend's temperament, ethics, and personal elegance, you need to look at him under the tests of severe circumstances, not under the regular rosy glow of daily life. Can you assess the danger a criminal poses by examining only what he does on an ordinary day? Can we understand health without considering wild diseases and epidemics? Indeed the normal is often irrelevant."

"It is remarkable how fast and how effectively you can construct a nationality with a flag, a few speeches, and a national anthem; to this day I avoid the label "Lebanese," preferring the less restrictive "Levantine" designation."

"History is opaque. You see what comes out, not the script that produces events, [...] The generator of historical events is different from the events themselves, much as the minds of the gods cannot be read just by witnessing their deeds."

"Categorizing is necessary for humans, but it becomes pathological when the category is seen as definitive, preventing people from considering the fuzziness of boundaries, let alone revising their categories."

"But it remains the case that you know what is wrong with a lot more confidence than you know what is right."

"We tend to use knowledge as therapy."

"The casino is the only human venture I know where the probabilities are known, Gaussian (i.e., bell-curve), and almost computable."

"Probability is a liberal art; it is a child of skepticism, not a tool for people with calculators on their belts to satisfy their desire to produce fancy calculations and certainties."

"There is no effective difference between guessing a variable that is not random, but for which information is partial or deficient (...), and a random one (...). In this sense, guessing (what I don't know, but what someone else may know) and predicting (what has not taken place yet) are the same thing."

"Cumulative errors depend largely on the big surprises, the big opportunities. Not only do economic, financial, and political predictors miss them, but they are quite ashamed to say anything outlandish to their clients — and yet events, it turns out, are almost always outlandish."

"Don't cross a river if it is four feet deep on average."

"Forecasting by bureaucrats tends to be used for anxiety relief rather than for adequate policy making."

"The same past data can confirm a theory and its exact opposite! If you survive until tomorrow, it could mean that either a) you are more likely to be immortal or b) that you are closer to death."