. gross ton-miles decreased 3% ( 3 % ) , while revenue ton-miles were flat in 2008 compared to 2007 with commodity mix changes ( notably autos and coal ) explaining the variance in year over year growth between the two metrics . operating ratio 2013 operating ratio is defined as our operating expenses as a percentage of operating revenue . our operating ratios improved 1.3 points to 76.0% ( 76.0 % ) in 2009 and 2.0 points to 77.3% ( 77.3 % ) in 2008