May's employment numbers also were up 2.33% from May 2011 levels, with all categories adding workers over the same month a year ago. Executives, officials, and staff assistants notched the biggest percentage gain, up 3.85%, over one year ago; Transportation (train and engine) workers also rose substantially, up 3.16%, compared with a year ago.

Compared with the previous month, however, three of six categories saw slippage, the largest within Maintenance of way and structures, off 1.41%. Transportation (other than train and engine) employment fell 0.9% from the previous month, as did Maintenance of equipment and stores, off 0.48%; Transportation (train and engine) declined a modest 0.08%.