Year	% of revenue
1972	38.83850204798119
1973	39.79126679462579
1974	41.28784143575588
1975	44.56090201683349
1976	43.04034197168043
1977	47.40915208613727
1978	47.920114337295026
1979	48.212827438909386
1980	47.91649655698009
1981	44.009093987326395
1982	47.33123861748763
1983	46.18649123106019
1984	44.52914662552571
1985	40.56514832560605
1986	37.84451061214544
1987	37.77416365321354
1988	37.41674926886817
1989	36.565809695342814
1990	37.62657024447147
1991	37.35703888542311
1992	37.75244761859714
1993	38.59708038853523
1994	39.15398959662384
2012	42.6237243172437
2013	42.2339006508941
2014	41.898511515278095
2015	41.70090778786431
2016	42.667277582039084
2017	43.20128153589397
2018	42.33044220105218
2019	43.764361527519426
2020	46.62743897861725
2021	43.515910276473655
2022	40.424003441030685