Year	% of revenue
1972	39.7606780167264
1973	43.581916471972576
1974	47.09144156867409
1975	42.40335756997277
1976	39.67416135625827
1977	37.7893852981909
1978	36.89374929777911
1979	35.15824651071358
1980	35.20346666075086
1981	35.039566790903685
1982	34.930538424976085
1983	32.920204795204796
1984	34.78060335755899
1985	36.42443955203975
1986	36.974522967449545
1987	36.97666280488012
1988	38.13837931721204
1989	38.35479826760884
1990	36.382745413471
1991	37.47168143796056
1992	37.1533583207088
1993	37.63016217196659
1994	38.7455375993244
1995	40.889829978199764
1996	39.924070497911465
1997	40.059582513373115
1998	37.962153657897034
1999	37.75658010952129
2000	38.297993191816076
2001	35.16121247976087
2002	35.02678686586932
2003	35.70570604706854
2004	36.56815508934329
2005	38.79963420181545
2006	37.21202049492542
2007	41.95584697865826
2008	41.535131871738166
2009	42.03344928538564
2010	41.25996098728762
2011	40.3490291748822
2012	41.86684023920791
2013	43.23873207150072
2014	48.04958079412544
2015	45.28388682571672
2016	44.66995052140189
2017	45.15424943327633
2018	42.87297354675103
2019	47.46561434838976
2020	46.64355442021713
2021	48.71098265347826
2022	45.39837568629048