  A representative investor generates realistic and complex security price
paths by following this trading strategy: if, a few ticks ago, the market asset
had two consecutive upticks or two consecutive downticks, then sell, and
otherwise buy. This simple, unique, and robust model is the smallest possible
deterministic model of financial complexity, and its generalization leads to
complex variety. Compared to a random walk, the minimal model generates time
series with fatter tails and more frequent crashes, thus more closely matching
the real world. It does all this without any parameter fitting.
