The mandatory disclosure of trades and market liquidity

Financial market regulations require various 'insiders' to disclosetheir trades after the trades are made. We show that such mandatorydisclosure rules can increase insiders' expected trading profits.This is because disclosure leads to profitable trading opportunitiesfor insiders even if they possess no private information onthe asset's value. We also show that insiders will generallynot voluntarily disclose their trades, so for disclosure tobe forthcoming, it must be mandatory. Key to the analysis isthat the market cannot observe whether an insider is tradingon private information regarding asset value of is trading forpersonal portfolio reasons.