A simple model is better than no model when it makes useful predictions over a well defined domain. The main problem with most models of market economics is th

A simple model is better than no model when it makes useful predictions over a well defined domain. The main problem with most models of market economics is that they only work when nothing interesting is happening. Probably the best, as in most practically useful, idea from market economics has been that of arbitrage freedom. And even that falls apart in low liquidity scenarios which often characterise severe events.