["There is substantial evidence that perks hurt a company's bottom line. David Yermack, an economist at N.Y.U. who specializes in executive compensation, looked at the performance of more than two hundred big American companies between 1993 and 2002, comparing those which allowed their C.E.O.s to use company jets for personal purposes with those which did not. Even after accounting for a host of other factors, Yermack found that the long-term stock-market performance of perk-rich companies was dramatically worse than that of their peers, costing shareholders hundreds of millions of dollars a year."]