Year	% of expense
1972	23.021171923043134
1973	21.580618605198165
1974	20.08468135924438
1975	19.520819362311773
1976	16.65269023723862
1977	17.40504778240627
1978	17.89153009717373
1979	17.563163823624077
1980	18.389805965826817
1981	18.667517776821104
1982	19.158057301097028
1983	20.28817609152125
1984	20.538938042888947
1985	20.64625426124553
1986	20.984598459845984
1987	20.558505256463377
1988	20.347971377719663
1989	20.151910349104934
1990	17.845502843052607
1991	17.694518360830227
1992	17.32776617954071
1993	15.868012771200807
1994	15.19510177064372
1995	13.979995792614124
1996	13.082486099587632
1997	13.116597320762885
1998	12.83978121979395
1999	12.781088164618303
2000	12.803922422237218
2001	7.293195177508031
2002	8.095064606029666
2003	8.994317384386322
2004	9.681374918337415
2005	9.58055638765805
2006	9.678425641262827
2007	9.357184269211473
2008	9.770680690495292
2009	9.489595043480055
2010	9.770116320332924
2011	9.40755583428169
2012	9.193992220054078
2013	8.243445763280471
2014	7.663159829085248
2015	7.292128250595262
2016	7.0530254279262
2017	6.953497405012868
2018	7.155537727085528
2019	7.415797015443848
2020	5.689831506111111
2021	5.7535589702841
2022	6.897667099208332