Year	% of revenue
1972	1.6476932294787274
1973	1.850362027353185
1974	1.7049180327868798
1975	1.9945778466305175
1976	1.672507167887857
1977	1.9885550786838426
1978	2.3701462430660625
1979	2.1653752255599192
1980	1.7877790625278018
1981	2.003572260619713
1982	2.0922459893048106
1983	2.0686356570608617
1984	2.48474280732345
1985	2.662422956451448
1986	2.8368794326241105
1987	2.613968393603325
1988	2.5557899177388754
1989	2.7678903805789865
1990	2.8179403733213655
1991	3.328152170055714
1992	3.7093372973346717
1993	3.333903816532604
1994	3.5286746034363334
1995	3.2251222484458637
1996	3.261042822829315
1997	3.5784910657544846
1998	3.4564956241142406
1999	3.4949075512105807
2000	3.5162835082574837
2001	3.504415802399069
2002	3.615495106479788
2003	3.6040762374815722
2004	3.900663423015697
2005	3.9840926495680566
2006	3.80332948747467
2007	3.983426200239361
2008	3.8936078094613893
2009	4.149420013764075
2010	5.821557367015702
2011	4.441413351154946
2012	4.293809309928479
2013	4.494784443133692
2014	4.558975172523201
2015	4.62711707732917
2016	4.572934916552134
2017	4.631619231343728
2018	4.263225012092696
2019	5.041580387007589
2020	5.40004999286531
2021	6.027890809742033
2022	5.703459998555739