The heads of U.S. companies are finding fewer costs to cut, sending profit margins into the first 12-month contraction since 2009 and leaving investors increasingly dependent on economic growth to boost stocks, Bloomberg reported.

Companies in the Standard & Poor’s 500 index earned $81.93 a share in the last 12 months on sales of $919.39 a share, generating margins of 8.9 percent, according to data compiled by Bloomberg that excludes banks.

The measure, a key gauge for investors, slipped from 9 percent, the first decline after a three-year, 1.6 percentage point expansion, the biggest ever, Bloomberg said.

Bears say the contraction shows that executives have squeezed all they can from expenses and point out that stagnant profitability accompanied recessions in 2000 and 2007. Bulls say housing and employment data show that the American economy is picking up speed and that even if earnings contract, valuations are so low that share prices will build on the 109 percent rally since March 2009. Read more.