Year % of revenue 1996 12.145687290460225 1997 11.46987587042083 1998 7.903489784066312 1999 9.122141344873164 2000 7.435102984379766 2001 5.080372303196669 2002 5.35359340948823 2003 5.480088113337941 2004 5.507153061429807 2005 5.145668513588516 2006 4.079575632929325 2007 3.3931424736673743 2008 3.388181249446724 2009 2.0590215794451594 2010 2.3654072029911934 2011 2.2149833620071298 2012 2.044134056716303 2013 2.0873580284407103 2014 2.0680252436878885 2015 1.721218317669988 2016 1.829056449221122 2017 1.8776534109870777 2018 1.9846390359914063 2019 1.4593070460123405 2020 1.373824039226634 2021 2.0119576093108495 2022 1.9751606728999394