Assimilation Effects in Financial Markets

Eliezer Fich and Guosong Xu

An assimilation bias occurs when people’s evaluative judgement is positively influenced by a previously observed signal. We study this effect by examining investors’ appraisal of M&A deals announced one day after other firms in the same 1-digit SIC as the merging parties release earnings surprises. Consistent with assimilation effects, acquirers’ M&A announcement stock return initially correlates with the previous day’s  earnings surprises. This effect reverses after one week. Assimilation generates other distortions as more positive surprises are related to increases in bid competition, takeover premiums, and withdrawn M&As. Evidence from IPOs corroborates the presence of assimilation effects in financial markets.