adjusted net income of $ 4.6 billion translated into adjusted earnings of $ 5.79 per diluted share , a best- ever performance .f0b7 freight revenues 2013 our freight revenues increased 7% ( 7 % ) year-over-year to $ 19.8 billion driven by volume growth of 2% ( 2 % ) , higher fuel surcharge revenue , and core pricing gains .growth in frac sand , coal , and intermodal shipments more than offset declines in grain , crude oil , finished vehicles , and rock shipments .f0b7 fuel prices 2013 our average price of diesel fuel in 2017 was $ 1.81 per gallon , an increase of 22% ( 22 % ) from 2016 , as both crude oil and conversion spreads between crude oil and diesel increased in 2017 .the higher price resulted in increased operating expenses of $ 334 million ( excluding any impact from year- over-year volume growth ) .gross-ton miles increased 5% ( 5 % ) , which also drove higher fuel expense .our fuel consumption rate , computed as gallons of fuel consumed divided by gross ton-miles in thousands , improved 2% ( 2 % ) .f0b7 free cash flow 2013 cash generated by operating activities totaled $ 7.2 billion , yielding free cash flow of $ 2.2 billion after reductions of $ 3.1 billion for cash used in investing activities and $ 2 billion in dividends , which included a 10% ( 10 % ) increase in our quarterly dividend per share from $ 0.605 to $ 0.665 declared and paid in the fourth quarter of 2017 .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 gaap by sec regulation g and item 10 of sec regulation s-k and may not be defined and calculated by other companies in the same manner .we believe free cash flow is important to management and investors 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', '2017', '2016', '2015'], ['cash provided by operating activities', '$ 7230', '$ 7525', '$ 7344'], ['cash used in investing activities', '-3086 ( 3086 )', '-3393 ( 3393 )', '-4476 ( 4476 )'], ['dividends paid', '-1982 ( 1982 )', '-1879 ( 1879 )', '-2344 ( 2344 )'], ['free cash flow', '$ 2162', '$ 2253', '$ 524']]
2018 outlook f0b7 safety 2013 operating a safe railroad benefits all our constituents : our employees , customers , shareholders and the communities we serve .we will continue using a multi-faceted approach to safety , utilizing technology , risk assessment , training and employee engagement , quality control , and targeted capital investments .we will continue using and expanding the deployment of total safety culture and courage to care throughout our operations , which allows us to identify and implement best practices for employee and operational safety .we will continue our efforts to increase detection of rail defects ; improve or close crossings ; and educate the public and law enforcement agencies about crossing safety through a combination of our own programs ( including risk assessment strategies ) , industry programs and local community activities across our network .f0b7 network operations 2013 in 2018 , we will continue to align resources with customer demand , maintain an efficient network , and ensure surge capability of our assets .f0b7 fuel prices 2013 fuel price projections for crude oil and natural gas continue to fluctuate in the current environment .we again could see volatile fuel prices during the year , as they are sensitive to global and u.s .domestic demand , refining capacity , geopolitical events , weather conditions and other factors .as prices fluctuate , there will be a timing impact on earnings , as our fuel surcharge programs trail increases or decreases in fuel price by approximately two months .lower fuel prices could have a positive impact on the economy by increasing consumer discretionary spending that potentially could increase demand for various consumer products that we transport .alternatively , lower fuel prices could likely have a negative impact on other commodities such as coal and domestic drilling-related shipments. .

Question: what was the percentage change in free cash flow from 2015 to 2016?
Answer: 330%