Pershing Square Capital Management LP owes its ability to amass an undetected stake of almost 10 percent in Allergan Inc. to a regulation it lobbied to preserve three years ago.
Pershing Square, the hedge-fund firm led by Bill Ackman, recruited a group of large investors in 2011 that persuaded the Securities and Exchange Commission to reconsider reducing a 10-day window that investors have to disclose stakes of five percent or more in a company. The SEC had successfully pushed for authority to shorten the reporting requirement in the 2010 Dodd-Frank Act.
