Examine the theory of adverse selection using 28.2 million Hong Kong IPO investors share applications. Two distinct regulatory regimes (discretionary against mandatory clawback provision) are tested. We find that, prior to the implementation of the regulation; uninformed investors benefit the least from the IPO market. The mandatory clawback provision has enhanced the fairness in IPO share allocations and reduced the winner’s curse problem. The Hong Kong regulator should resist the deregulation pressure to scrap the clawback provision