Year	% of revenue
1975	8.777429467084634
1976	9.340659340659348
1977	7.80022446689113
1978	7.589696412143493
1979	7.658802177858448
1980	7.541157727031317
1981	7.506872488898317
1982	7.336496103015911
1983	8.179780876494007
1984	9.408290264740026
1985	9.524634167460388
1986	4.06671664167915
1987	3.7001160899264884
1988	3.8191467968042523
1989	2.8628495339547166
1990	3.522801593435992
1995	3.2616180811743547
1996	2.93367570243464
1997	2.7916763962878
1998	2.6574086060734445
1999	2.7912931714957576
2000	2.6512885217730555
2001	2.7492532605829987
2002	2.8996237580295743
2003	2.919113211012212
2004	2.7095032239362857
2005	2.8099675000618425
2006	2.958107434655148
2007	2.9030413828920425
2008	2.898255071609826
2009	2.8707779863656695
2010	2.774059543404981
2011	2.532670379303512
2012	2.827162554319766
2013	2.2997671433650066
2014	2.2311899956667833
2015	2.2098650714107735
2016	2.264438261140065
2017	2.4606813398538807
2018	2.4587251634582743
2019	2.5212757650335598
2020	2.553383923013638
2021	2.4855249537264754
2022	2.428277133442064