Year	% of expense
1972	44.853574504737246
1973	40.94716494845361
1974	39.784946236559
1975	40.16741790083709
1976	38.76417495950016
1977	38.28085451047886
1978	37.67670048228835
1979	40.97805377178742
1980	38.98041320096584
1981	39.78881050623355
1982	39.07509391298014
1983	35.483034737023985
1984	37.53716690042076
1985	36.30816549260845
1986	38.85647896376131
1987	36.02093166427248
1988	33.995876437821046
1989	32.73879598122867
1990	30.669850112747
1991	31.341227973094288
1992	30.254911970110026
1993	31.866006820261187
1994	32.533007694144004
1995	40.52598980418315
1996	41.037030521593806
1997	40.44782087165134
1998	37.155106839084425
1999	37.706635241742774
2000	37.41648106904231
2001	35.539545136835315
2002	35.22130904049906
2003	36.107449946651606
2004	36.22425306138917
2005	34.661390904781
2006	35.119894417496525
2007	35.13738417961561
2008	34.279661627588595
2009	35.682335830520564
2010	34.67426130295479
2011	34.358987240028135
2012	33.658330327940206
2013	32.2678643916875
2014	25.851144814662995
2015	29.78518274546311
2016	30.51624876032767
2017	30.787099647488837
2018	27.30284911243163
2019	29.64418216493348
2020	28.88826011341006
2021	27.78571942798858
2022	28.851162635370038