Year	% of revenue
1972	1.4647968494861183
1973	1.4612399900932842
1974	1.801351974189586
1975	2.0696728817905337
1976	2.421996492737321
1977	2.730282139277792
1978	2.8263337116912686
1979	3.0665748636195116
1980	3.3169677464821876
1981	4.0351693132239195
1982	4.689548945736115
1983	5.484556962025315
1984	5.364326375711579
1985	5.360977282159571
1986	5.350967136476611
1987	5.3386319438572665
1988	5.4040262711725005
1989	4.9589036933501545
1990	4.970626818000348
1991	5.593659436199175
1992	6.775076845931065
1993	6.754614296984271
1994	7.035444132651699
1995	7.709496043676562
1996	7.687844152802984
1997	7.566042445256952
1998	7.595986125204772
1999	7.005968360040043
2000	7.037491256849454
2001	6.735377625458382
2002	6.616721503527007
2003	6.087209767300789
2004	6.097194373250938
2005	5.948236974952928
2006	5.800703630357135
2007	5.842882525158793
2008	5.838049086823598
2009	5.566324610164139
2010	5.1633683733850235
2011	5.399308420712033
2012	4.820874767339016
2013	3.5656375905282154
2014	3.1551986066780002
2015	2.7292886725946826
2016	2.2790185050697374
2017	1.9243204839677186
2018	1.7289342501599827
2019	1.462855463296348
2020	1.064802322912178
2021	0.9761583614571745
2022	1.4766526964173698