Year	% of expense
1972	2.0354605389489855
1973	1.8532818532818531
1974	1.963084976758879
1975	2.218490020700699
1976	2.011968633924887
1977	2.6433898752557585
1978	2.549703072553576
1979	2.446811776624812
1980	2.575345669268321
1981	2.9288347037142044
1982	2.6279426816786082
1983	2.4284433242044545
1984	2.2111414453645
1990	3.5287612714587704
1991	3.4987149583448054
1992	3.9739349521636185
1993	3.6681746009005534
1994	4.518075411327256
1995	4.481065349644437
1996	3.9433452059965566
1997	4.037851723529387
1998	4.279203437324013
1999	4.320238275470093
2000	4.1856585038826655
2001	4.17466165778513
2002	3.7184122272132005
2003	3.4586606977535927
2004	3.465158820568871
2005	3.8779215836484235
2006	4.337653882984904
2007	3.880568729932528
2008	3.5573913975888467
2009	2.982890827973695
2010	2.7585656854115905
2011	2.5112595643132822
2012	2.2613946677164853
2013	1.951637306580881
2014	1.8036778552845207
2015	1.6887610853353254
2016	1.4580351400524365
2017	1.2294157354124102
2018	1.0034845030984663
2019	0.9023299097986403
2020	0.67720402262885
2021	0.577696514217263
2022	0.7116124124850961