Year	% of revenue
1972	27.39532210284295
1973	26.587662219637174
1974	26.77266241518882
1975	28.985657597842124
1976	30.366199700605456
1977	29.176810561526363
1978	27.480984021233812
1979	28.013690384053003
1980	25.966625966626
1981	25.87858539087516
1982	24.689495650424952
1983	23.785897024132538
1984	22.9386204832334
1985	23.80916139466294
1986	24.264170187964424
1987	25.42271750098715
1988	24.835417493714466
1989	24.742140018700308
1990	24.70709532289811
1991	24.748191875675964
1992	26.60294746413085
1993	26.678224448165384
1994	25.81634849185599
1995	28.622209441931712
1996	28.18908038554506
1997	27.418083626997046
1998	27.40601569653924
1999	27.82563840011432
2000	27.080211054686824
2001	28.57150339502534
2002	28.998449827365796
2003	29.74789115896351
2004	29.77940804348081
2005	29.100504553231755
2006	28.60527977373496
2007	28.156278451907074
2008	28.760870482433514
2009	30.518168582676203
2010	29.663787181367752
2011	29.855951222691097
2012	29.855125279126742
2013	29.446307359195227
2014	28.92165362592734
2015	29.267448807276857
2016	29.15168373625337
2017	29.765830750465543
2018	28.739476302489248
2019	29.29754635197201
2020	30.807783997235493
2021	29.141263729418053
2022	29.067525218418943