Year	% of revenue
1972	17.38885762521103
1973	17.575187969924812
1974	16.11905682257441
1975	14.526382708200892
1976	14.6918013165769
1977	15.360904187002312
1978	15.828367103694873
1979	16.840597503580927
1980	15.789473684210526
1981	13.825830447608054
1982	14.214711729622268
1983	13.388203017832648
1984	13.963845952318573
1985	13.781575037147103
1986	13.879550475458649
1987	14.466671815864679
1988	19.47892609699769
1989	19.592616168045833
1990	15.997090420769918
1991	16.19057181585421
1992	15.799725530125283
1993	15.223349350418225
1994	20.172319474835888
1995	20.239103831309425
1996	16.99177562210038
1997	16.789108141313342
1998	14.881384025691494
1999	16.352591123233324
2000	18.043115405411758
2001	18.413192760319607
2002	18.524216524216524
2003	24.750347999757913
2004	23.632181389999452
2005	23.407392080283476
2006	22.206974873420716
2007	23.255548147442614
2008	21.73983012963791
2009	26.207927576254647
2010	26.202879108781318
2011	25.269620875427627
2012	23.72004040385233
2013	23.71579329709135
2014	23.574429020502407
2015	23.169443507677045
2016	22.898755337119855
2017	19.784602255301493
2018	21.08846504846273
2019	18.114305681215228
2020	20.42780404292826
2021	20.815950789006898
2022	20.16899267799601