Year	% of revenue
1973	16.474970324587648
1974	19.690447553332984
1975	20.696040520668845
1976	23.742637063887656
1977	25.98566308243726
1978	27.479866430956683
1979	27.068114302629205
1980	29.358161648177568
1981	32.817360900806634
1982	34.198973697643844
1983	34.965828967155076
1984	35.88630348042503
1985	36.18054184096648
1986	37.52272999145344
1987	36.43658734243412
1988	35.93374706026986
1989	36.02239386346141
1995	32.25190365113075
1996	33.76955823462167
1997	34.253295872055325
1998	34.0212817039859
1999	34.65345462186876
2000	35.26734285541052
2001	35.58732388546874
2002	33.79281410795579
2003	32.22041866136577
2004	32.543930451640726
2005	33.1420598434151
2006	34.63800562574693
2007	35.33159061018155
2008	35.47494384447518
2009	32.88617369755777
2010	33.195375711493334
2011	32.620481501345544
2012	33.237322147723134
2013	33.488555135641704
2014	32.72396083457471
2015	32.70388705263
2016	32.16207162727021
2017	32.14628981956212
2018	31.38561751941881
2019	31.773745886749648
2020	33.09284141760671
2021	31.943703440889536
2022	32.165812807760766