Year	% of revenue
1972	10.02805683772287
1973	10.655706655555134
1974	8.39066469093988
1975	9.567051681115426
1976	8.394014374926357
1977	8.041395170563433
1978	8.405604789662418
1979	9.63105683859713
1980	9.992258863601176
1981	11.784824018852996
1982	13.74034437699522
1983	15.265044744259873
1984	15.722806995254762
1985	18.418797015014835
1986	19.667262848850946
1987	18.103740036787247
1988	15.611322309552131
1989	13.634522569095536
1990	9.78043815078672
1991	7.281645478274854
1992	5.895247757156214
1993	4.4012114547057335
1994	3.1783635271908612
1995	1.7883319797939556
1996	1.158644055414007
1997	1.7598726588758025
1998	1.1469634387247394
1999	6.021006893265437
2000	7.386424141620564
2001	7.078005811184954
2002	7.639021370296605
2003	5.832411317050435
2004	6.674628967708074
2005	6.059916754312237
2006	7.153532829859453
2007	5.625386264969884
2008	4.910323709536308
2009	5.782252830815573
2010	6.1378035823220465
2011	5.94727979021965
2012	5.966279974920638
2013	5.3451548266205675
2014	5.603919123399824
2015	4.794203010914434
2016	4.180746954750744
2017	4.806842355438929
2018	5.135538239388595
2019	5.183886947072978
2020	4.992466031039465
2021	6.6573176185405964
2022	7.024439770887518