Year	% of revenue
1972	36.69862192929903
1973	37.838562617323696
1974	37.04918032786889
1975	40.68551510457009
1976	39.980885632367006
1977	42.01716738197417
1978	42.246596066565765
1979	42.92537947139382
1980	40.736458240683184
1981	39.97049002096767
1982	40.30748663101605
1983	41.16345808920236
1984	41.65758500435904
1985	41.618672324947084
1986	41.234708934266315
1987	41.76806416430656
1988	42.00459818603673
1989	42.92471585283745
1990	43.17225900572328
1991	42.80918414422087
1992	43.40235765893462
1993	43.693308232072525
1994	42.84206707779572
1995	46.35934872815339
1996	45.58937499885491
1997	44.57093254848776
1998	40.230901447889515
1999	40.17198254017558
2000	40.378961072201044
2001	40.08440665532591
2002	41.000591802201264
2003	42.15980797017559
2004	41.62214367333646
2005	41.587376227647084
2006	41.464165459270575
2007	41.44749749847947
2008	41.547803289981985
2009	43.75405192447712
2010	41.878246322643825
2011	42.49690364696785
2012	42.258731251582766
2013	41.994292910774924
2014	42.26547072845913
2015	42.01924755810729
2016	42.07077791966024
2017	41.628730448976725
2018	40.25749316977763
2019	38.368267694332175
2020	38.52902898365385
2021	38.062766194187226
2022	37.80365778349124