Year	% of revenue
1973	32.33618233618245
1974	32.348679077025864
1975	32.20208252988808
1976	31.115574525064922
1977	30.997669348169254
1978	30.29016769883785
1979	30.05885015844279
1980	29.48294180144017
1981	27.99220272904487
1982	27.196630692287467
1983	24.170686825483724
1984	23.0854713243465
1985	22.760457321272813
1986	24.060016075734517
1987	25.41103478838909
1988	26.316473800545996
1989	27.307408852473277
1990	30.555212577684486
1991	31.53891596514556
1992	29.73486205661046
1993	30.66959837839689
1994	26.29006903150854
1995	25.816588236200218
1996	26.44986449864499
1997	26.108776597616686
1998	25.784166286220696
1999	25.184518451845182
2000	25.008529512111906
2001	25.735005555033524
2002	26.42109281273858
2003	24.53016231974149
2004	23.684863651875368
2005	25.90496902661399
2006	25.5292159236576
2007	26.774048257372655
2008	25.14793369393412
2009	25.98957760538716
2010	26.07405766058547
2011	24.88849961857788
2012	23.32925014264567
2013	22.650851431391906
2014	24.055402713215067
2015	26.51370299553856
2016	26.593037715370073
2017	29.4653624547769
2018	29.035381238817635
2019	30.625578078937355
2020	30.500341621458237
2021	31.247992546015908
2022	32.85584410451006