By Meena KrishnamsettyNEW YORK ( Insider Monkey) -- Academic studies have shown that stocks intensively bought by insiders tend to outperform the market by more than 7 percentage points a year. We have been publishing the lists of such companies for the past three weeks. The stocks that insiders bought like crazy managed to beat the market during the first two weeks. Last week we listed four stocks with the top insider purchases. Here are how the four performed: 1. Town Sports International Holdings ( CLUB): We've said that CLUB is one of the top stocks with insider purchases for the past six weeks. It's one of the two stocks Insider Monkey added to its hypothetical (and public) portfolio in mid November. When we added it to our portfolio the stock was trading at $3.01. On Thursday, the stock closed at $3.98. The stock is up 7.3% since last Thursday's close, beating the S&P 500 ETF ( SPY) which returned 1.15%. 2. World Heart ( WHRT): We said World Heart is a very illiquid stock and that we were staying away from this one. The investors who didn't follow our advice returned 5.5% since Dec. 16. 3. Bank of America ( BAC): This is another stock with persistent insider buying. Initially in November, two insiders made substantial purchases at around $12.50. We weren't very keen on Bank of America then. At the beginning of December another director purchased BAC shares at around $11.30. We said: "This is nearly 10% less than the price paid by previous insiders. We weren't enthusiastic about the previous purchases but we believe this is a better point to monkey insider buys." We were lucky or right. Since then, BAC shares have been outperforming the market. Bank of America shares returned 4.3% since Dec. 16, beating the market by more than 3 percentage points. 4. Scientific Games ( SGMS): "Jim Cramer didn't recommend buying SGMS last week in 'Mad Money.' Nevertheless, we are sticking with the insiders here." That's what we said about SGMS on Dec. 16. Scientific Games returned 4.8% since then, beating the market by more than 3.5 percentage points. All four of the stocks Insider Monkey highlighted on Dec. 16 outperformed the market by a huge margin. Excluding WHRT, the average return of these stocks was 5.5%, beating the market by 4.3 percentage points in one week. The stocks with significant insider purchases managed to beat the market a third time in a row. Thirteen out of the 16 stocks we picked managed to beat the S&P 500 index, usually by a huge margin. We will keep providing weekly updates on stocks insiders buy like crazy, although it might be better to follow them in real-time if one is monkeying insider transactions.