The CareerCast.com/JobSerf Employment Index, which measures managerial recruitment activity online, lost ground in May with a decline of 10.1 points over April 2011. Even with the loss, the May 2011 Index is still 11.5 points higher than a year ago. The Index is also 43.9 points higher than it was in May 2009. Riverside, which is ranked at the bottom of the Index for managerial hiring, had a gain of nine percent over last month. The other cities that showed an increase in hiring were Nashville (+four percent) and Houston (+two percent). Atlanta has the biggest loss of jobs this month (-nine percent), followed by Hartford (-eight percent) and Detroit (-seven percent). The sharpest decline this month was for C-level executives, who experienced a 27-point drop in hiring over last month. “While Manager-level jobs remain strong, the weakness in the demand for C-level jobs could be due to a slowdown in hiring over the summer months,” said Jay Martin, COO of JobSerf.  ”Businesses will need more senior executives to lead them out of the recession, which should result in increased hiring once the economy heats back up.”