{"pre_text": ["other operating/performance and financial statistics we report key railroad performance measures weekly to the association of american railroads ( aar ) , including carloads , average daily inventory of rail cars on our system , average train speed , and average terminal dwell time .", "we provide this data on our website at www.up.com/investors/reports/index.shtml .", "operating/performance statistics included in the table below are railroad performance measures reported to the aar : 2008 2007 2006 % (  % ) change 2008 v 2007 % (  % ) change 2007 v 2006 ."], "post_text": ["average train speed 2013 average train speed is calculated by dividing train miles by hours operated on our main lines between terminals .", "ongoing network management initiatives , productivity improvements , and lower volume levels contributed to 8% ( 8 % ) and 2% ( 2 % ) improvements in average train speed in 2008 and 2007 , respectively .", "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 improved 1% ( 1 % ) and 8% ( 8 % ) in 2008 and 2007 , respectively .", "lower volumes combined with initiatives to more timely deliver rail cars to our interchange partners and customers improved dwell time in both periods .", "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 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 .", "in 2007 , revenue ton-miles declined 1% ( 1 % ) in relation to the 1% ( 1 % ) reduction in carloadings compared to 2006 .", "gross ton-miles decreased 2% ( 2 % ) in 2007 driven by a mix shift in freight shipments .", "operating ratio 2013 operating ratio is defined as our operating expenses as a percentage of operating revenue .", "our operating ratios improved 2.0 points to 77.3% ( 77.3 % ) in 2008 and 2.2 points to 79.3% ( 79.3 % ) in 2007 .", "price increases , fuel cost recoveries , network management initiatives , and improved productivity more than offset the impact of higher fuel prices .", "employees 2013 productivity initiatives and lower volumes reduced employee levels throughout the company in 2008 versus 2007 .", "fewer train and engine personnel due to improved network productivity and 5% ( 5 % ) lower volume drove the change while productivity initiatives within the support organizations also contributed to a lower full-time equivalent force level .", "lower employee levels in 2007 versus 2006 ."], "table": [["", "2008", "2007", "2006", "% (  % ) change 2008 v 2007", "% (  % ) change 2007 v 2006"], ["average train speed ( miles per hour )", "23.5", "21.8", "21.4", "8 % (  % )", "2 % (  % )"], ["average terminal dwell time ( hours )", "24.9", "25.1", "27.2", "( 1 ) % (  % )", "( 8 ) % (  % )"], ["average rail car inventory ( thousands )", "300.7", "309.9", "321.6", "( 3 ) % (  % )", "( 4 ) % (  % )"], ["gross ton-miles ( billions )", "1020.4", "1052.3", "1072.5", "( 3 ) % (  % )", "( 2 ) % (  % )"], ["revenue ton-miles ( billions )", "562.6", "561.8", "565.2", "-", "( 1 ) % (  % )"], ["operating ratio", "77.3", "79.3", "81.5", "2.0 pt", "2.2 pt"], ["employees ( average )", "48242", "50089", "50739", "( 4 ) % (  % )", "( 1 ) % (  % )"], ["customer satisfaction index", "83", "79", "72", "4 pt", "7 pt"]], "table_ori": [["", "<i>2008</i>", "<i>2007</i>", "<i>2006</i>", "<i>% Change 2008 v 2007</i>", "<i>% Change 2007 v 2006</i>"], ["Average train speed (miles per hour)", "23.5", "21.8", "21.4", "8 %", "2 %"], ["Average terminal dwell time (hours)", "24.9", "25.1", "27.2", "(1)%", "(8)%"], ["Average rail car inventory (thousands)", "300.7", "309.9", "321.6", "(3)%", "(4)%"], ["Gross ton-miles (billions)", "1,020.4", "1,052.3", "1,072.5", "(3)%", "(2)%"], ["Revenue ton-miles (billions)", "562.6", "561.8", "565.2", "-", "(1)%"], ["Operating ratio", "77.3", "79.3", "81.5", "2.0 pt", "2.2 pt"], ["Employees (average)", "48,242", "50,089", "50,739", "(4)%", "(1)%"], ["Customer satisfaction index", "83", "79", "72", "4 pt", "7 pt"]]}

Question: based on the operating/performance statistics what was the average operating ratio from 2006 to 2008
Evidence:
table_6: the operating ratio of 2008 is 77.3 ; the operating ratio of 2007 is 79.3 ; the operating ratio of 2006 is 81.5 ; the operating ratio of % ( % ) change 2008 v 2007 is 2.0 pt ; the operating ratio of % ( % ) change 2007 v 2006 is 2.2 pt ;
Program: add(77.3, 79.3), add(#0, 81.5)
Answer:
str_answer: 79.4
exe_answer: 238.1