Year	% of revenue
1972	7.143858992940297
1973	6.579486759039107
1974	5.99020243498307
1975	5.626993107704969
1976	5.410531730212821
1977	4.678031833239073
1978	4.35701082651175
1979	3.7943596250665137
1980	4.411225910456511
1981	6.358336329107988
1982	5.478995163808918
1983	5.384803771505541
1984	5.157868359505513
1985	4.506917682734222
1986	3.947416380137777
1987	3.5182783407707015
1988	3.6381769637532853
1989	3.2086379054990206
1990	3.2128514056224895
1991	3.609554195050444
1992	3.8982728185248
1993	3.840156417900801
1994	4.106129505054681
1995	10.741002478520029
1996	10.476921782713566
1997	10.275639898828615
1998	9.96381595797618
1999	9.952781371319427
2000	9.340049554151896
2001	9.530837186377465
2002	10.4223382302458
2003	10.572729088996876
2004	10.4661104386257
2005	10.14485412437195
2006	9.456424965414381
2007	8.695969906507205
2008	8.017931751630712
2009	8.839059443497218
2010	9.01654673232879
2011	8.709465616610856
2012	8.525583751746254
2013	8.384493960843185
2014	8.47561254448095
2015	8.377463317077742
2016	8.37921518950505
2017	8.20755796656256
2018	8.26316951456672
2019	8.15583565961343
2020	7.809514944559961
2021	7.723758390574183
2022	7.948601105076445