Bill Ackman Admits To 'Very Costly' Mistakes

Bill Ackman and his Pershing Square hedge fund were both large winners throughout 2014. The same can't be said for 2015.

According to Reuters, Ackman's Pershing Square fund lost between 16 to 20 percent in 2015. In fact, he even admitted to investors that he made several errors throughout the difficult year.

Specifically, Ackman said it was a "very costly" mistake when he decided to hold on to shares of Valeant Pharmaceuticals Intl Inc VRX above the $200 per share mark.

Ackman added that when shares of Valeant began to tumble, so did the rest of the fund's portfolio. He continued that the fund's holdings "went into free fall which continued up until the present."

Ackman acknowledged he should have cut its stake in Canadian Pacific Railway Limited CP after the Toronto-listed issue topped C$240 per share.

Ackman also pointed out it was a mistake to buy additional shares of Platform Specialty Products Corp PAH at $25 per share to help the company finance an acquisition.