Year	% of revenue
1972	5.871779508687835
1973	5.819254491820868
1974	6.29508196721311
1975	6.216111541440749
1976	6.355527237973877
1977	5.464949928469234
1978	5.118507312153298
1979	4.8614796730708125
1980	8.414124344036306
1981	9.714995728818842
1982	9.331550802139045
1983	9.231137151739784
1984	8.892763731473414
1985	9.038092351217559
1986	8.762911133323794
1987	8.15406435281392
1988	8.807508964353515
1989	8.103045423943604
1990	8.396625893090931
1991	9.113169381454275
1992	9.237044975282613
1993	9.163101146671247
1994	8.449032087854091
1995	7.919925339750413
1996	7.638780741177742
1997	7.005740780845603
1998	6.422021492993613
1999	5.701744347627066
2000	4.976293209003683
2001	5.645072429423387
2002	5.7181772492201
2003	4.989199787805871
2004	5.362833150374947
2005	5.5157125391302015
2006	5.45637028113778
2007	5.8897319939571116
2008	6.015806457014235
2009	6.268015479598249
2010	6.945629561056771
2011	6.28918910904865
2012	5.880228869898811
2013	5.779038934676678
2014	5.7671594310596035
2015	5.600895617431673
2016	5.623519285074799
2017	5.377098858057203
2018	5.13600220249578
2019	4.895747587729917
2020	4.277171812749701
2021	6.75511782167265
2022	6.537644883311685