Year	% of revenue
1982	10.791800643086818
1984	12.409408773045136
1985	9.251785159888232
1986	9.508020431938345
1988	8.810672722111837
1989	9.060402684563758
1990	10.743042802655742
1991	11.196576253542306
1992	11.795440151994933
1993	10.430889759373251
1994	9.957928909795607
1995	9.499495006172147
1996	8.652472620910142
1997	6.965445117434312
1998	10.637683131343103
1999	6.82403559093836
2000	10.817647209881615
2001	6.342173315651278
2002	10.407235084161856
2003	17.383219587458694
2004	7.232258240557251
2005	11.785021325918954
2006	12.287512834146776
2007	8.85298216033002
2008	10.228491722656399
2009	10.38537036365403
2010	12.257004729832548
2011	14.926060281104716
2012	19.531100001840823
2013	23.034830787233293
2014	16.7947845664126
2015	19.26796282039023
2016	18.044893585439006
2017	20.614805837499368
2018	23.60009814556988
2019	25.316809268186752
2020	17.929384703777316