Does this include part-time workers? If so, the slight increase since 2011 could just be a reflection of the lower unemployment and underemployment. Actually

Does this include part-time workers? If so, the slight increase since 2011 could just be a reflection of the lower unemployment and underemployment. Actually even if it's only considering full-time employees, it could still be related to unemployment, since a tighter labor market would leave more positions unfilled, which would mean more overtime.