Year	% of revenue
1972	11.539505837632365
1973	12.000454562672829
1974	12.51323031329382
1975	15.697270599130503
1976	16.041003888299752
1977	15.6439248754312
1978	18.071813342179677
1979	17.882156898482048
1980	17.388656654796925
1981	18.360401902314937
1982	20.20857799758506
1983	18.2712569442544
1984	19.756576314468845
1985	20.221776006233704
1986	20.057031012722305
1987	17.525444512568978
1988	19.37635562189519
1989	20.169496241833603
1990	23.769449113069367
1991	25.501738094158107
1992	27.29585645799765
1993	27.76430747209203
1994	29.710070429984963
1995	30.877808594208894
1996	31.69673433604559
1997	31.633504915573525
1998	28.375923011102543
1999	28.76205244589103
2000	29.845007428893073
2001	28.1660643678425
2002	29.79036829802777
2003	28.692922490687483
2004	31.98621387193833
2005	32.81475964799915
2006	36.58183197524541
2007	37.054686338779256
2008	38.97090988626422
2009	37.838871442034936
2010	33.22232105880072
2011	38.019747958565816
2012	36.862099175202275
2013	35.407530528105866
2014	33.77271163215539
2015	31.688571121866126
2016	30.89696314888611
2017	30.15659329102343
2018	30.50566587631917
2019	31.7035741958869
2020	30.13084677310608
2021	30.90596933706934
2022	33.53273625142027