A fun, readable history of the influence of physics on finance. Well-written and flows very well, essentially a collection of vignettes. The thesis is relatively simple but in our days contrarian-financial models should not be abandoned, but used with an eye towards improvement and with some knowledge of their limitations.
The book is an interesting exploration of both the financial ideas that physicists brought to wall street (Weatherall does a good job of explaining the ideas in non-technical terms), as well as the sociology of physics and finance. For example, the "father" of modern mathematical finance, a frenchman named Bachelier, laid down the foundations of finance almost a century ago (including random walk, Brownian motion, normally distributed price, martingales and even a proto-EMH. He argued that prices were random because news is random, and prior knowledge is already "priced in"), but because the application of math to finance was unfashionable at the time (at the time the academic circles focused on abstract math), his work never received the support or wide-spread recognition it should have. In contrast, Osborne, another physicist turned financial mathematician came of age after the synthesis of basic research and industrial support (Dupont's nylon and the Manhattan Project) already occurred, allowing his somewhat aimless research to occur. Similarly, Black of Black-Scholes became so celebrated because at the time, the powers that be were looking to start a derivatives market, and the end of the Bretton Woods system created floating exchange rates that would led to an explosion of currency derivatives. Similarly, Weatherall argues that Malaney's proposal to use gauge theory (a physics concept) to measure inflation, was sunk by academics who were tasked with ad hocing a method to measure CPI with the goal of reducing social security payouts. Weatherall thinks that physicists can be very useful in this sense, by injecting fresh ways and more nuanced understanding into the "old boy's club" of economic academia. A particularly promising example is the importation of how tanks explode and when bubbles burst (both study how the appearance of coordination between random fissures can lead to catastrophic failure similar to herding behavior, what Sornette calls dragon king theory, the idea that dragon kings can be predicted by certain periodic indica). Another example cited, the enormous success of Renaissance, which hires no economics or finance students, only those trained in mathematics and physics (though the secrecy of how Renaissance makes its money, makes discussions of its strategies rather speculative [a similar complaint occurs for "more money than god"]. This is the same complaint I have about the chapter on the "prediction company". Weatherall discusses how the hedge fund made money applying chaos theory concepts, such as attractors and initial conditions to pioneer black box statistical modeling [mostly off of statistical correlations without conjectures about underlying models], but admits that the firm is rather secretive [making the firm's success itself...a black box].).
I particularly liked the treatment of the simplifying assumptions found in models. There is I think, a tendency for detractors and pundits to dismiss a model by its assumptions alone. Weatherall makes the good point that the process of modeling is iterative, and that good modelers recognize their assumptions and improve on them. This happened with Edward Thorp, who improved on a blackjack model by realizing that cards dealt were not independent but actually dependent on the deck (starting the tactic of cardcounting). More dramatic is the story of the normal curve. Bachelier assumed that prices were normally distributed, but this lead to oddities such as negative prices. Osborne recognized that it was not prices, but returns that were normally distributed, implying a log-normal price distribution. Mandelbrot argued that actual market returns are not normal distributions but levy-stable distributions with fatter tails than the normal distribution (later research indicated that this, was also not technically correct), and as a consequence did not converge towards an average (reviewed also of course, is Mandelbrot's work on fractals and measurement theory). Weatherall makes the good point that, financial academia properly set aside Mandelbrot's discovery and used the simplifying assumption that returns were normally distributed in order to build more knowledge. At the time, it was unclear how to incorporate or even work with Mandelbrot's levy-stable distributions. However, as Weatherall notes, the market's volatility smile after 87' (which Weatherall interprets as the market's belief that out the money options were worth more than what Black-Scholes predicted) and O'Connor's modifications to the Black-Scholes model were indications that practitioners had indeed considered challenging the normal distribution assumption. By doing so, they played the role of "smart money" that EMH assumes.
The book concludes with three lessons about finance. 1) The best models are not ignorant of human nature but attempt to incorporate them (despite behavioral economics attacks on models, they themselves often produce models). For example, Osborne's conjecture that returns were log-normal was inspired by an old psychological experiment that people changes in sensations based on the starting sensation. 2) The misuse of models does not justify their wholesale abandonment, only that the limitations of models be recognized and improved on (contra Taleb). 3) Complicated financial instruments such as derivatives are tools, that be used correctly for good or incorrectly for bad.
A somewhat miscellaneous fact I find interesting, is the idea to only bet a fraction of wealth by advantage/payout as an optimal betting strategy.
A great book for anyone looking for a nuanced but non-technical view of finance, and a good counterweight to the very opinionated pundits that seem to have sprung up post-2008 like daisies. Not to mention, very enjoyable to read, both in readability and entertainment value.