Year	% of revenue
1975	1.7162471395881007
1976	1.672507167887857
1977	2.305422772356857
1978	2.3114198404360673
1979	2.222724303615986
1980	1.7109437697580294
1981	2.8297683192013494
1982	2.79295843769038
1983	2.3675071283842026
1984	2.8241513633834066
1985	3.271086278051026
1986	2.4990895567530185
1987	2.7730123375234226
1988	2.821459425385392
1991	2.362482445945081
1992	2.151698330454807
1993	2.6608125761653096
1994	2.0879936474286636
1995	2.4607384841640845
1996	2.528727062436741
1997	2.4891206743620824
1998	2.274435996713184
1999	2.4441675452889866
2000	1.713297567380513
2001	1.4590098743955469
2002	1.4072716451381726
2003	1.8816732741194673
2004	1.7702912201871464
2005	1.4453931088019525
2006	1.6583776106715746
2007	1.5039532096274066
2008	1.5447067516719892
2009	1.5817297296342026
2010	1.430099116120196
2011	1.288297775011167
2012	1.2101352246549295
2013	1.6061445008364343
2014	2.052722136348741
2015	2.2098650714107735
2016	1.6621670014542247
2017	2.086817820591857
2018	1.644292652046739
2019	2.2170680027054157
2020	1.8742439675873752
2021	1.2285238694172331
2022	1.6738171202288143