Year	% of revenue
1975	17.13688610240334
1976	17.73940345368918
1977	17.39618406285067
1978	18.307267709291526
1979	21.451905626134334
1980	19.251194901752495
1981	21.632480439839348
1982	22.41613012538118
1983	23.344123505976082
1984	23.615652357346292
1985	25.06710537708892
1986	16.79160419790103
1987	16.052793739268527
1988	19.078728489439424
1989	21.19980377041134
1990	21.389499970271693
1995	22.280653272965075
1996	23.32594372824729
1997	23.18361560315873
1998	22.771235676485706
1999	23.12773726721679
2000	24.508575085268745
2001	23.498984877338653
2002	22.2389491750308
2003	20.172870952975146
2004	20.67747318924987
2005	20.110036805283595
2006	20.79028771572405
2007	22.417645690959922
2008	22.757066745030343
2009	21.644019071192737
2010	21.256623850883543
2011	22.958542936123678
2012	21.25211679037962
2013	25.89886559962497
2014	25.236397210943455
2015	25.2793192746128
2016	24.089697830427383
2017	24.019105658202253
2018	24.148645738439882
2019	23.3213836722418
2020	23.605064267398536
2021	22.053703084090117
2022	24.89718964038497