The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.NEW YORK ( Insider Monkey) -- Academic research has shown that insider purchases on average outperformed the market over the following 12-month period. On the other hand, insider sales are usually not informative. This is because most insider sales are motivated by diversification or liquidity needs. Therefore, insider sales really do not mean much compared with insider purchases. However, recent research on insider sales has shown that stocks sold under the 10b5-1 plans have large negative abnormal returns. The magnitude of the abnormal returns is about 70 basis points per month calculated by using Carhart's four factor model. In this article, we are going to discuss a few large-cap stocks that insiders are selling like crazy under 10b5-1 plans in the past week. All companies have at least $5 billion market cap. Follow TheStreet on Twitter and become a fan on Facebook.