Year	% of expense
1972	35.08771929824561
1973	34.72222222222222
1974	32.38095238095238
1975	34.05797101449276
1976	36.11111111111111
1977	38.75
1978	37.83783783783784
1979	35.148514851485146
1980	34.1130604288499
1981	39.85239852398524
1982	24.10323709536308
1983	19.183983781044095
1984	21.73686947477899
1985	20.337995337995338
1986	15.838251792595484
1987	12.356497642782596
1988	13.845010788584455
1989	16.60405282331512
1990	18.871764346273267
1991	27.20352133232958
1992	31.383463953496115
1993	22.08877961924639
1994	22.693488738124753
1995	18.88242919860703
1996	18.558212439918666
1997	15.341461852897616
1998	17.758092094724727
1999	17.916487614441685
2000	17.090872245844835
2009	12.58184545165077
2010	12.306233459368116
2011	12.040498036647513
2012	11.973245294063355
2013	12.02421299295896
2014	11.801834586006756
2015	12.086003285440663
2016	11.691601029473182
2017	11.317801494677566
2018	10.988679705555509
2019	10.450920461112464
2020	10.853210440821961
2021	10.517965313044996
2022	9.323083002092654