Year	% of expense
1972	31.932773109243694
1973	25.13089005235602
1974	22.65349329569513
1975	24.731823599523242
1976	23.273273273273272
1977	30.175739391341622
1978	28.996809641970934
1979	26.594492821840433
1980	25.637692932575142
1981	23.990850376749194
1982	23.163492456096957
1983	21.8052738336714
1984	21.624828845276127
1985	21.587129708407456
1986	24.064954079595367
1987	26.05619567414595
1988	26.013153773880365
1989	27.068912077693973
1990	24.242424242424242
1991	26.553208137715178
1992	26.630302632011304
1993	27.778344064466076
1994	22.92212556335814
1995	20.053015542163216
1996	23.068002681693816
1997	13.66961831609243
1998	11.775979805928113
1999	10.649526387009473
2002	7.426203257871513
2003	14.558385768775134
2004	12.73333602438232
2008	12.35254041241585
2009	14.818309921278852
2010	15.3952603895368
2011	14.935624506029626
2012	14.708484177191666
2013	15.104243316163846
2014	14.336541491923022
2015	16.64236806105804
2016	16.376549471514988
2017	15.943529673757576
2018	15.610959791018091
2019	16.238012606391834
2020	14.771668196631385
2021	14.617050402821327
2022	25.22808298838386