Year	% of revenue
1972	46.337280960291515
1973	44.02778101475284
1974	42.41682475572691
1975	43.71736673066226
1976	44.3476551275653
1977	46.33132489337215
1978	44.50827205882353
1979	42.18056931226045
1980	39.335561736112886
1981	37.95467273487733
1982	37.75288900398148
1983	37.159497904167935
1984	37.307224182291584
1985	38.809931659618506
1986	39.42050713773548
1987	41.03455389777464
1988	37.615847708820446
1989	35.70465451140129
1990	33.683897212025
1991	33.87269464042579
1992	36.8645710854827
1993	37.79276049849749
1994	38.4640428612635
1995	35.62077976481384
1996	34.35431986822356
1997	34.570041966761
1998	36.67688268030289
1999	34.8271610267305
2000	27.520929485612942
2001	27.813206057068296
2002	27.909572755012363
2003	27.67723556398837
2004	26.361390395515738
2005	24.72000124202388
2006	23.40813394495087
2007	24.226801074064653
2008	21.27770678907978
2009	24.546341480276148
2010	24.927160417123105
2011	23.154803483069227
2012	22.84845392726082
2013	24.067926000339757
2014	24.640298435420586
2015	25.9490775281753
2016	27.38675977986948
2017	26.865334499851073
2018	25.207190308245963
2019	25.08584786774041
2020	27.81726506252675
2021	22.472734219620445
2022	15.12186173768402