Year	% of revenue
1975	2.561662925393658
1976	3.1534279068201325
1978	4.091641353416061
1979	5.0726121490343505
1980	6.263267393186486
1981	5.143322785456668
1982	6.0479627129166955
1983	6.8103433480796385
1984	7.392170164343378
1985	8.907663345424503
1986	9.395373760828765
1987	9.576837416481052
1988	9.546376577449875
1989	9.654637990317202
1990	10.282813171422667
1991	8.26065935457039
1992	9.685759129326176
1993	9.574637184232396
1994	9.924045450173743
1995	8.971489542305193
1996	8.756771770765342
1997	10.166831411744385
1998	9.685930612807525
1999	8.059328052201657
2000	7.925765041522509
2001	7.074629905205288
2002	6.616721503527007
2003	6.014558570593073
2004	5.586808823073184
2005	4.7917358571939
2006	4.389276695351052
2007	4.191168459174837
2008	4.001612727508087
2009	5.566324610164139
2010	5.467907050027081
2011	5.658798978816325
2012	5.999762564366986
2013	5.796226221956222
2014	5.3885969155140145
2015	5.018650162335846
2016	4.606503210148726
2017	4.138206670579482
2018	3.6565205360512665
2019	3.2941030151271233
2020	3.1527278314899014
2021	2.925854653669411
2022	2.959561570914396