interest expense 2013 interest expense increased in 2014 versus 2013 due to an increased weighted- average debt level of $ 10.8 billion in 2014 from $ 9.6 billion in 2013 , which more than offset the impact of the lower effective interest rate of 5.3% ( 5.3 % ) in 2014 versus 5.7% ( 5.7 % ) in 2013 . interest expense decreased in 2013 versus 2012 due to a lower effective interest rate of 5.7% ( 5.7 % ) in 2013 versus 6.0% ( 6.0 % ) in 2012 . the increase in the weighted-average debt level to $ 9.6 billion in 2013 from $ 9.1 billion in 2012 partially offset the impact of the lower effective interest rate . income taxes 2013 higher pre-tax income increased income taxes in 2014 compared to 2013 . our effective tax rate for 2014 was 37.9% ( 37.9 % ) compared to 37.7% ( 37.7 % ) in 2013 . higher pre-tax income increased income taxes in 2013 compared to 2012 . our effective tax rate for 2013 was 37.7% ( 37.7 % ) compared to 37.6% ( 37.6 % ) in 2012 . other operating/performance and financial statistics we report a number of key performance measures weekly to the association of american railroads ( aar ) . we provide this data on our website at www.up.com/investor/aar-stb_reports/index.htm . operating/performance statistics railroad performance measures are included in the table below : 2014 2013 2012 % (  % ) change 2014 v 2013 % (  % ) change 2013 v 2012 .
if average train speed ( miles per hour ) increased at the same rate as carloadings , what would the speed have been for 2014?
average train speed 2013 average train speed is calculated by dividing train miles by hours operated on our main lines between terminals . average train speed , as reported to the association of american railroads , decreased 8% ( 8 % ) in 2014 versus 2013 . the decline was driven by a 7% ( 7 % ) volume increase , a major infrastructure project in fort worth , texas and inclement weather , including flooding in the midwest in the second quarter and severe weather conditions in the first quarter that impacted all major u.s . and canadian railroads . average train speed decreased 2% ( 2 % ) in 2013 versus 2012 . the decline was driven by severe weather conditions and shifts of traffic to sections of our network with higher utilization . average terminal dwell time 2013 average terminal dwell time is the average time that a rail car spends at our terminals . lower average terminal dwell time improves asset utilization and service . average terminal dwell time increased 12% ( 12 % ) in 2014 compared to 2013 , caused by higher volumes and inclement weather . average terminal dwell time increased 3% ( 3 % ) in 2013 compared to 2012 , primarily due to growth of manifest traffic which requires more time in terminals for switching cars and building trains . gross and revenue ton-miles 2013 gross ton-miles are calculated by multiplying the weight of loaded and empty freight cars by the number of miles hauled . revenue ton-miles are calculated by multiplying the weight of freight by the number of tariff miles . gross ton-miles , revenue ton-miles and carloadings all increased 7% ( 7 % ) in 2014 compared to 2013 . gross ton-miles and revenue ton-miles declined 1% ( 1 % ) in 2013 compared to 2012 and carloads remained relatively flat driven by declines in coal and agricultural products offset by growth in chemical , autos and industrial products . changes in commodity mix drove the year-over-year variances between gross ton- miles , revenue ton-miles and carloads. .