. the plan has two purchase periods , the first from october 1 through march 31 and the second from april 1 through september 30 . for the years ended december 31 , 2014 , 2013 and 2012 , employees purchased 1.4 million , 1.5 million and 1.4 million shares , respectively , at purchase prices of $ 51.76 and $ 53.79 , $ 43.02 and $ 50.47 , and $ 34.52 and $ 42.96 , respectively