In a paper published as a lead article in the Journal of Finance in 1990, Professor Nejat Seyhun investigated whether informed investors stabilize and correct mistakes in security prices by buying undervalued assets and selling overvalued assets or destabilize security prices by jumping into already overpriced securities to create bigger bubbles and mis-valuations first, only to exploit them later. Seyhun's investigation centered on the stock market crash of Oct. 19, 1987, when the stock market crashed by 22% in one day. He found that top corporate insiders bought undervalued stocks and sold overvalued stocks in record quantities immediately following the crash. Hence, informed insiders were stabilizing security prices and not destabilizing them further. This finding provides comfort that the stock market will be self-policing and self-correcting and justifies the current regulatory system, which assumes that more information is beneficial by requiring timely, accurate, and full dissemination of information from all parties involved. Seyhun was among the first to explore various aspects of reported insider trading and its effects on share prices and shareholder wealth.