Corporate insiders tend to buy more shares when they have valuable information not yet known to the public, as shown by a study analyzing insider trading data from 1986 to 2012. This study introduced a new measure called relivol, which tracks how much a company's stock price moves unexpectedly. Insiders tend to sell fewer shares when relivol is high, likely due to reasons other than insider information. When insiders buy shares during high relivol periods, they tend to make higher profits compared to selling shares during the same time frame.