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 .

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
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 .

Question: based on the operating/performance statistics what was the average operating ratio from 2006 to 2008
Answer: 79.4
Calculation: add(77.3, 79.3), add(#0, 81.5)