Year	% of expense
1978	14.925925925925936
1979	12.68105232042562
1980	15.109829154648349
1981	15.991068361387828
1982	14.032600992204083
1983	11.886833046471606
1984	12.326755392381832
1985	18.10094759234191
1986	14.557383771592624
1987	9.071307772829309
1988	7.969770051776434
1989	5.682276947920867
1990	36.44785090016823
1991	36.20223765604415
1992	35.056412618006036
1993	37.315898625610735
1994	42.073613271124906
1995	35.169731116718836
1996	36.3917105755271
1997	36.47065964246184
1998	36.00941209237267
1999	36.688088279161875
2000	37.09716866996898
2001	37.25951366378587
2002	37.780461396199364
2003	39.973845965206394
2004	39.860414268491326
2005	40.392517805200804
2006	40.94988375674777
2007	41.2795661281144
2008	41.181458189928954
2009	42.938366880560864
2010	42.5336995335058
2011	42.76468319935634
2012	44.37379299200318
2013	44.69396348768224
2014	41.738448013326646
2015	44.176595807859144
2016	45.665952501963154
2017	43.650296837147025
2018	45.550452236396225
2019	46.02697872652313
2020	47.02187331227819
2021	47.71382909252858
2022	47.35152600986835