Year	% of revenue
1972	61.419897244278374
1973	64.6991622239147
1974	68.43960269144505
1975	65.67505720823799
1976	66.14449380406828
1977	67.6116504854369
1978	64.71317280453258
1979	65.45507841125604
1980	67.32308474145597
1981	66.830819739407
1982	66.54766154944663
1983	63.641021262061315
1984	60.99948856579236
1985	61.944230655378604
1986	59.30277536021661
1987	51.11353547513355
1988	53.57817885335211
2001	53.78843903580622
2002	52.22856560825245
2003	52.942916495970415
2004	52.71442124507243
2005	54.9259311328956
2006	58.17246624535433
2007	56.66803322249048
2008	59.45357103388105
2009	55.99073108950433
2010	50.96345889199161
2011	45.41852137072727
2012	48.95021065521035
2013	50.30833856328416
2014	50.319982483871975
2015	51.55513338097906
2016	51.89272937470159
2017	52.81477338942675
2018	53.305831586262784
2019	54.17212614820861
2020	53.49823463674311
2021	55.150479931418175
2022	58.258782233977236