ZIP traders: ZIP traders were proposed as an improvement to ZIC traders when it was shown that the apparent convergence of the ZIC traders' prices to the theoretical market equilibrium was due to the particular market structure of the ZIC experiments, and that such convergence could not be reproduced in other markets. ZIP stands for Zero Intelligence Plus. Like the ZIC algorithm, ZIP traders generate stochastic bids within a budget constraint, but they also use an elementary form of machine learning to adjust their current offer/bid based upon observed market activity. In experiments similar to those used to test the ZIC traders, the performace of ZIP traders emulated human data significantly more closely than had the ZICs. These results suggest ZIP traders as a beginning of the investigation of the minimal intelligence required in a trading algorithm to achieve theoretical equilibrium in market structures of varying complexity. (Cliff and Bruten, 1998)