Year	% of revenue
1988	28.322589073529002
1989	24.97397691099162
1990	24.86700336264182
1991	27.064471158888697
1992	30.84389427274988
1993	35.99351495775422
1994	35.2125228356263
1995	37.24012774577899
1996	36.5283148225191
1997	36.82858837903821
1998	38.38617147250656
1999	36.4493963445711
2000	36.199748363282346
2001	30.67257617623992
2002	32.23622506500488
2003	28.85490515696754
2004	29.428519047800464
2005	26.24274840341226
2006	26.189712740231034
2007	25.595467854104086
2008	24.838599410156057
2009	26.21377407432502
2010	29.16287171968544
2011	28.72784714189018
2012	30.111065675847275
2013	29.344098878654467
2014	29.00273518330075
2015	30.891009873450496
2016	31.798766658458923
2017	33.9949996084823
2018	33.128418694379555
2019	34.54299860735896
2020	45.81187114057624