Year	% of revenue
1972	40.32165422171166
1973	43.212435233160626
1974	46.623923061510716
1975	48.940523162355696
1976	41.750405186385734
1977	44.674512140622674
1978	37.63250883392226
1979	38.46153846153847
1980	31.16608520985305
1981	28.482877756325575
1982	23.8700219887613
1983	26.31045320896279
1984	28.158415841584155
1985	33.69811979742709
1986	29.588626986396505
1987	39.079410614160906
1988	40.311985151508836
1989	40.60209168214251
1990	40.051152993954645
1991	42.998911582047505
1992	44.169268987016366
1993	43.290045345552095
1994	38.10508895324783
1995	36.38201130979673
1996	36.551721662473035
1997	35.93011384009832
1998	36.80515193651308
1999	39.173895697028236
2000	42.42553821357499
2001	30.786008939312087
2002	31.634311014866928
2003	20.86542647974799
2004	28.002067587951814
2005	22.954998976363473
2006	13.659360491717617
2007	9.454657614708156
2008	9.522848765594986
2009	8.833070234101271
2010	8.175779253745546
2011	7.229006669579833
2012	6.627835828744686
2013	5.970109395258718
2014	5.994306410348497
2015	5.506766708469294
2016	6.286583579972123
2017	6.122909150705465
2018	6.094589875912898
2019	5.662183101238019
2020	4.88090809551728
2021	5.50322084461685
2022	5.877561022711894