Year	% of revenue
1972	8.640822045773003
1973	7.616146230007616
1974	7.081063761614867
1975	7.723112128146453
1976	8.580780921206452
1977	9.009708737864077
1978	10.463881019830028
1979	11.109482632273194
1980	11.332740439588363
1981	12.342259156663589
1982	13.173866476258478
1983	17.20604559815558
1984	18.48469350478556
1985	19.548872180451127
1986	19.678947877381297
1987	18.614099766759463
1988	16.628988622465997
2001	5.953896559794056
2002	4.852225522335211
2003	5.008430834736598
2004	4.714865792257006
2005	4.509351913253818
2006	3.8514011510294974
2007	3.422463140952641
2008	1.9441616984150065
2009	3.314767971008799
2010	3.8020836724283678
2011	4.478646976099351
2012	5.010273332918249
2013	4.9808030040134375
2014	4.457507480636743
2015	4.375947626603868
2016	4.035352813586169
2017	3.769899436514436
2018	3.5609435339887314
2019	3.2933437191705743
2020	3.0744995743401313
2021	2.7790937589293976
2022	3.16844434778101