Year	% of revenue
2001	23.23675895678252
2002	26.213897099480516
2003	19.68061770641397
2004	20.95467073778322
2005	14.867890294675112
2006	13.208703266825928
2007	14.58346824774363
2008	13.077792597136945
2009	15.45436407299056
2010	15.987195968750942
2011	14.364412908275693
2012	15.181670510531681
2013	14.77948368911592
2014	11.88122794625201
2015	14.481870215039597
2016	14.89209553856749
2017	18.696534445331068
2018	18.457319866221294
2019	20.84680227421551