Asymmetric information, imitative behaviour and communication: price formation in an experimental asset market

The paper describes experimental results from a simulated stock market with manipulation of asymmetric information and communication, including conditions intended to promote imitative behaviour and rumour. Price discovery was inefficient when the presence of insiders was disguised, compared to a homogeneous expectations baseline. When the presence of insiders was revealed observed prices became efficient with respect to bad news but not with respect to good news, possibly suggesting loss-averse behaviour. With free communication there was a decrease in both efficiency and price volatility—insider information was masked by noise. Price formation under these conditions was similar to baseline, but with weak evidence of speculative pricing. It is conjectured that other factors than informational noise may be necessary determinants of herd behaviour, but further work is indicated.