. commodity mix changes ( notably automotive shipments ) drove the variance in year-over-year growth between gross ton-miles , revenue ton-miles and carloads . operating ratio 2013 operating ratio is our operating expenses reflected as a percentage of operating revenue . our operating ratio increased 0.1 points to 70.7% ( 70.7 % ) in 2011 versus 2010 . higher fuel prices , inflation and weather related costs , partially offset by core pricing gains and productivity initiatives , drove the increase