Year	% of revenue
1973	33.83815644058794
1974	34.00645692220047
1975	30.16720222210122
1976	29.462042262223516
1977	28.893776474421607
1978	25.35716624107901
1979	25.696947912592023
1980	26.355153788932366
1981	25.71373509897307
1982	24.441041347626246
1983	25.00054170946166
1984	26.012720736380512
1985	25.270830715093563
1986	24.03786338067675
1987	23.972305283491664
1988	30.242962437288494
1989	30.189958994764766
1995	22.437220545008728
1996	21.187298514824867
1997	21.34882213097039
1998	24.412578764501504
1999	24.706725967777228
2000	24.62668144927285
2001	23.514853530554063
2002	23.74878221458438
2003	22.892480327463918
2004	23.420860309845878
2005	23.77165386730308
2006	23.67614902488793
2007	22.747921949500192
2008	21.650692651420076
2009	21.065174776594393
2010	22.755201687352343
2011	23.362110590859118
2012	23.57299792879921
2013	23.36733818854472
2014	24.217624441378803
2015	23.911281276640295
2016	24.245641630620003
2017	24.43744064543339
2018	24.451318163465256
2019	24.19358374043438
2020	22.645303514095836
2021	23.812448947980887
2022	23.21865707298559