operating expenses millions 2014 2013 2012 % (  % ) change 2014 v 2013 % (  % ) change 2013 v 2012 .
what percentage of total operating expenses was fuel in 2014?
operating expenses increased $ 718 million in 2014 versus 2013 . volume-related expenses , incremental costs associated with operating a slower network , depreciation , wage and benefit inflation , and locomotive and freight car materials contributed to the higher costs . lower fuel price partially offset these increases . in addition , there were approximately $ 35 million of weather related costs in the first quarter of operating expenses increased $ 336 million in 2013 versus 2012 . wage and benefit inflation , new logistics management fees and container costs for our automotive business , locomotive overhauls , property taxes and repairs on jointly owned property contributed to higher expenses during the year . lower fuel prices partially offset the cost increases . compensation and benefits 2013 compensation and benefits include wages , payroll taxes , health and welfare costs , pension costs , other postretirement benefits , and incentive costs . volume-related expenses , including training , and a slower network increased our train and engine work force , which , along with general wage and benefit inflation , drove increased wages . weather-related costs in the first quarter of 2014 also increased costs . general wages and benefits inflation , including increased pension and other postretirement benefits , and higher work force levels drove the increases in 2013 versus 2012 . the impact of ongoing productivity initiatives partially offset these increases . fuel 2013 fuel includes locomotive fuel and gasoline for highway and non-highway vehicles and heavy equipment . volume growth of 7% ( 7 % ) , as measured by gross ton-miles , drove the increase in fuel expense . this was essentially offset by lower locomotive diesel fuel prices , which averaged $ 2.97 per gallon ( including taxes and transportation costs ) in 2014 , compared to $ 3.15 in 2013 , along with a slight improvement in fuel consumption rate , computed as gallons of fuel consumed divided by gross ton-miles . lower locomotive diesel fuel prices , which averaged $ 3.15 per gallon ( including taxes and transportation costs ) in 2013 , compared to $ 3.22 in 2012 , decreased expenses by $ 75 million . volume , as measured by gross ton-miles , decreased 1% ( 1 % ) while the fuel consumption rate , computed as gallons of fuel consumed divided by gross ton-miles , increased 2% ( 2 % ) compared to 2012 . declines in heavier , more fuel-efficient coal shipments drove the variances in gross-ton-miles and the fuel consumption rate . purchased services and materials 2013 expense for purchased services and materials includes the costs of services purchased from outside contractors and other service providers ( including equipment maintenance and contract expenses incurred by our subsidiaries for external transportation services ) ; materials used to maintain the railroad 2019s lines , structures , and equipment ; costs of operating facilities jointly used by uprr and other railroads ; transportation and lodging for train crew employees ; trucking and contracting costs for intermodal containers ; leased automobile maintenance expenses ; and tools and supplies . expenses for purchased services increased 8% ( 8 % ) compared to 2013 primarily due to volume- 2014 operating expenses .