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) - Insider trading is most profitable when several insiders buy around the same time. Academic studies have shown that insider purchases beat index funds by more than 7 % per year when there are several insiders purchasing. During the past two trading days, there were eight stocks that caught the attention of Insider Monkey .

No 1. Town Sports Intl ( CLUB): This was one of our favorite stocks with insider trading about four months ago. We specifically wrote a separate article covering this stock and told our readers that we added it to our hypothetical portfolio. The stock gained around 57% since we wrote that article. There were more insider purchases last week.

No. 2. Ligand Pharma ( LGND): There were several insider purchases after the company announced its earnings mid-February. Tom Steyer's Farallon Capital started a new position in this stock during the fourth quarter. Dan Loeb's Third Point sold all of their LGND holdings during the fourth quarter.

No. 3. KKR Financial ( KFN): This is a large cap stock with substantial insider purchases. Leon Cooperman's Omega Advisors have a large KFN position. Dan Loeb also have some KFN shares in his portfolio.

No. 4. Transdigm ( TDG): Robert J. Small spent nearly $7 Million on TDG shares during the past couple of weeks. Chase Coleman's Tiger Global, Stephen Mandel's Lone Pine Capital, and Jonathan Auerbach's Hound Partners are among the tiger cubs with significant TDG holdings.

No. 5. Cenveo ( CVO): A director of the company, Robert G Burton, bought more than 65,000 shares below $6.

No. 6. Resource America ( REXI): Whitney Tilson is extremely bullish about REXI.

No. 7. Calgon Carbon ( CCC): William R. Newlin purchased 24,500 shares at $13.91.

No. 8. Ferro ( FOE): Timothy K. Pistell and Thomas R. Miklich bought 6,000 and 5,000 shares respectively. Pistell paid a 5% premium over Miklich's price by delaying his purchase by one day.

This article was originally published by Insider Monkey.

>To see these stocks in action, visit the 8 Stocks With Substantial Insider Buying portfolio on Stockpickr.