2022 fuel prices 2013 crude oil prices increased at a steady rate in 2007 , rising from a low of $ 56.58 per barrel in january to close at nearly $ 96.00 per barrel at the end of december .our 2007 average fuel price increased by 9% ( 9 % ) and added $ 242 million of operating expenses compared to 2006 .our fuel surcharge programs are designed to help offset the impact of higher fuel prices .in addition , our fuel conservation efforts allowed us to improve our consumption rate by 2% ( 2 % ) .locomotive simulator training , operating practices , and technology all contributed to this improvement , saving approximately 21 million gallons of fuel in 2007 .2022 free cash flow 2013 cash generated by operating activities totaled a record $ 3.3 billion , yielding free cash flow of $ 487 million in 2007 .free cash flow is defined as cash provided by operating activities , less cash used in investing activities and dividends paid .free cash flow is not considered a financial measure under accounting principles generally accepted in the united states ( gaap ) by sec regulation g and item 10 of sec regulation s-k .we believe free cash flow is important in evaluating our financial performance and measures our ability to generate cash without additional external financings .free cash flow should be considered in addition to , rather than as a substitute for , cash provided by operating activities .the following table reconciles cash provided by operating activities ( gaap measure ) to free cash flow ( non-gaap measure ) : millions of dollars 2007 2006 2005 .
[['millions of dollars', '2007', '2006', '2005'], ['cash provided by operating activities', '$ 3277', '$ 2880', '$ 2595'], ['cash used in investing activities', '-2426 ( 2426 )', '-2042 ( 2042 )', '-2047 ( 2047 )'], ['dividends paid', '-364 ( 364 )', '-322 ( 322 )', '-314 ( 314 )'], ['free cash flow', '$ 487', '$ 516', '$ 234']]
2008 outlook 2022 safety 2013 operating a safe railroad benefits our employees , our customers , our shareholders , and the public .we will continue using a multi-faceted approach to safety , utilizing technology , risk assessment , quality control , and training for , and engaging with our employees .we plan to implement total safety culture ( tsc ) throughout our operations .tsc , an employee-focused initiative that has helped improve safety , is a process designed to establish , maintain , and promote safety among co-workers .with respect to public safety , we will continue our efforts to maintain , upgrade , and close crossings , install video cameras on locomotives , and educate the public about crossing safety through various internal and industry programs , along with other activities .2022 commodity revenue 2013 despite uncertainty regarding the u.s .economy , we expect record revenue in 2008 based on current economic indicators , forecasted demand , improved customer service , and additional opportunities to reprice certain of our business .yield increases and fuel surcharges will be the primary drivers of commodity revenue growth in 2008 .we expect that overall volume will fall within a range of 1% ( 1 % ) higher to 1% ( 1 % ) lower than 2007 , with continued softness in some market sectors .2022 transportation plan 2013 in 2008 , we will continue to evaluate traffic flows and network logistic patterns to identify additional opportunities to simplify operations and improve network efficiency and asset utilization .we plan to maintain adequate manpower and locomotives , improve productivity using industrial engineering techniques , and improve our operating margins .2022 fuel prices 2013 fuel prices should remain volatile , with crude oil prices and conversion and regional spreads fluctuating throughout the year .on average , we expect fuel prices to increase 15% ( 15 % ) to 20% ( 20 % ) above the average price in 2007 .to reduce the impact of fuel price on earnings , we will continue to seek recovery from our customers through our fuel surcharge programs and expand our fuel conservation efforts. .

Question: what was the percentage increase in the cash provided by operating activities from 2006 to 2007
Answer: 13.8%