  We show, by studying in detail the market prices of options on liquid
markets, that the market has empirically corrected the simple, but inadequate
Black-Scholes formula to account for two important statistical features of
asset fluctuations: `fat tails' and correlations in the scale of fluctuations.
These aspects, although not included in the pricing models, are very precisely
reflected in the price fixed by the market as a whole. Financial markets thus
behave as rather efficient adaptive systems.
