Meager improvements since 2009 have barely kept up with a similarly tepid pace of inflation, raising the real value of compensation per hour by only 0.5 percent. Federal Reserve Chair Janet Yellen has zeroed in on faster wage growth as an important milestone for declaring the job market healed and ready to withstand policy tightening, even as other labor measures improve. Stagnant earnings also explain an economy that’s having trouble sustaining a rebound in housing and consumer spending, according to David Blanchflower, a professor of economics at Dartmouth College in Hanover, New Hampshire.