Year	% of revenue
1972	46.62376332724986
1973	47.55634442334675
1974	48.886157627900005
1975	50.99087878676861
1976	52.135790623035504
1977	51.30136362255894
1978	51.27695800227027
1979	51.50415761877017
1980	53.93831191712298
1981	54.94872987398401
1982	55.046520825094255
1983	54.70987341772169
1984	52.193548387096854
1985	52.15900683880989
1986	53.00568290436397
1987	53.61630168259064
1988	54.685519579924645
1989	52.87522219352488
1991	54.29151664178449
1992	53.6219752711077
1993	54.933477139078704
1994	55.06536674596918
1995	57.06300451581229
1996	59.287433666107646
1997	60.03723741550749
1998	59.52996809858268
1999	57.91110586824972
2000	57.09206733558956
2001	57.83980647214588
2002	58.287064732421044
2003	57.5288101270407
2004	59.02136218400672
2005	58.52291709325258
2006	57.19581994096181
2007	55.07786817439594
2008	54.67297645464115
2009	55.27682892616627
2010	55.54441858089171
2011	54.310415402388166
2012	54.40819017275433
2013	54.43928121215117
2014	54.35228728700744
2015	54.68485501984508
2016	55.32069411527883
2017	55.48462713299327
2018	55.42331223327722
2019	55.65591397849462
2020	58.09273928854773
2021	56.286827536914295
2022	56.032643845348716