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	12.682192531669607
1991	12.358780746134663
1992	12.098173663460418
1993	11.652158573406632
1994	11.37374900745748
1995	10.491116694163898
1996	10.07659132779164
1997	10.009019658086375
1998	10.045488771669431
1999	9.97447377471342
2000	10.092644931466488
2001	7.570409425096087
2002	8.179318538633213
2003	8.491246761404286
2004	8.894671199006105
2005	8.534836783462817
2006	8.834393959577856
2007	8.435294860536645
2008	8.64561136595572
2009	8.300265317137345
2010	8.559576967563618
2011	8.594517634516704
2012	8.391035743744755
2013	7.573447051401803
2014	7.3941891735981375
2015	7.208857699429241
2016	7.110476149241285
2017	7.265347088259457
2018	7.29796256147497
2019	7.266137364501915
2020	5.317659303636622
2021	5.927757361542961
2022	7.340458786699182