The study looked at how a trading ban in China affected insider trading by big shareholders in the stock market. It found that insider trading didn't happen during the ban because it was too risky. But, the ban only made insider trades less profitable during that time, while still being profitable outside the ban. Insider trading by informed shareholders before the ban was much more profitable than uninformed trading. The rules changed how insiders traded, but didn't stop them due to strict supervision and lack of legal action. This research helps us understand how big shareholders trade and has important lessons for regulators.