Year % of revenue 1995 19.684074701954028 1996 18.609787412382726 1997 16.756039912933275 1998 15.938731922622868 1999 14.86839943164793 2000 14.437360494650692 2001 14.002199191259415 2002 12.822118967950649 2003 11.92270007348567 2004 10.704901698059514 2005 9.830404908678341 2006 9.37428224562785 2007 9.033752796400131 2008 8.67051822406119 2009 8.526054705375042 2010 7.849746596713148 2011 7.6986774704713685 2012 7.51780698770443 2013 6.951230787832234 2014 6.826212441944045 2015 6.438307836920826 2016 6.259717286697616 2017 5.386651447004033 2018 4.742136461424088 2019 4.584950915602697 2020 4.5795931616155565 2021 3.8028487616934954 2022 3.3102634338276475