The Globe and Mail reports in its Tuesday, June 4, edition that Pershing Square Capital Management head Bill Ackman said Monday he plans to sell up to seven million Canadian Pacific Railway ($135.50) shares on the open market, a process that will take six to 12 months. The Globe's Richard Blackwell and Guy Dixon write that at current prices, those shares would be worth $950-million. Pershing acquired most of its interest in late 2011 for a little more than $1-billion. New York-based Pershing owned just over 24 million CP shares as of March 31, currently valued at about $3.25-billion, so the sale would represent more than a quarter of its holdings. Mr. Ackman says Pershing is selling shares because CP takes up too much of its portfolio. He says CP's "share price has more than tripled since we first invested in CP. ... As a result, our stake in CP has grown to approximately 26 per cent of the combined assets of our funds. Given that increased concentration, portfolio management considerations have driven our decision to trim our holdings. Even after these sales, we expect to remain CP's largest shareholder and for CP to remain one of our largest investments." Pershing owns about 14 per cent of all CP shares outstanding.