Greg Buch Despite last week's turbulence, several company insiders took advantage of the market weakness to aggressively add to their holdings. While it's not possible to know their motivation, studies have shown that stocks with significant insider buying tend to outperform over a 12 month period. I've combed through last week's SEC Form 4 reports and arrived at a list of four companies whose insiders made what I feel are the most significant purchases: SunEdison shares have been hit hard since the company announced the acquisition of rooftop solar developers Vivint Solar Inc (NYSE:VSLR) and Mark Group and posting disappointing quarterly results with a massive $256 million net loss that exceeded analyst estimates by a wide margin. Shares have dropped nearly 68% since hitting a 52-week high of $32.13 on June 23 and insiders apparently see value. Chairman Emmanuel Hernandez added 10,000 shares at an average price of $ 9.95 last Tuesday, bringing his total holdings to 79,000 shares. He also bought 20,000 shares on Aug. 21 with the purchases together representing a 61% increase to his holdings. CFO Brian Wuebbels also scooped up some shares on Aug. 21, adding 50,000 at an average price of $11.19, which was a 24% increase to his holdings. They were accompanied by directors Peter Blackmore, Clayton Daley, and Randy Zwirn, who added 8,700, 6,100, and 2,500 shares respectively. It's worth noting that these were the first purchases of the company's stock in years by the Chairman and a reversal in sentiment by the CFO, who sold shares at a much higher price last August. Investors buying shares in SunEdison are betting the company's aggressive expansion can eventually lead to profits and positive cash flow and hoping low natural gas prices, which have reduced the appeal of solar energy, will return to historical levels. Sotheby's shares have been hit hard recently due to fears that the slowdown in China will have a negative impact... More