Year	% of revenue
1972	13.791786055396383
1973	15.420328303763878
1974	14.64332460732985
1975	18.407662376534017
1976	17.293519695044512
1977	13.315217391304332
1978	15.311975995057873
1979	17.176746229316166
1980	20.98715659736225
1981	18.74815470918219
1982	17.451128117689038
1983	19.50391464006097
1984	19.9901182898828
1985	20.786949161237324
1986	19.24953095684811
1987	20.28919429427478
1988	19.630058235030564
1989	20.57316378819508
1990	21.76674364896078
1991	18.99305603489928
1992	18.311888831703573
1993	18.144864385067763
1994	19.505095886579372
1995	25.318970464880135
1996	24.719101123595504
1997	25.51352705410822
1998	27.121936640765092
1999	30.527465557943696
2000	29.470736994219653
2001	28.921927045251444
2002	29.096691108833344
2003	22.7364045722203
2004	18.462485146834155
2005	20.22760236527948
2006	23.89416622767516
2007	28.772909507445593
2008	27.858445422511075
2009	25.69957800855954
2010	24.776785714285715
2011	27.19618497764193
2012	26.494271118935615
2013	26.17940402618858
2014	23.69789780218188
2015	23.352032589124107
2016	23.695142894517097
2017	24.45315852297214
2018	24.143553390763152
2019	23.46261315522799
2020	24.619062722874204
2021	25.026630167111456
2022	25.654929465378025