Year	% of expense
1972	17.200151343170628
1973	16.287522717302682
1974	14.696223316912972
1975	14.176084649852934
1976	12.989406576550667
1977	11.828445747800586
1978	10.351170082636392
1979	10.350639335290317
1980	11.014395714763973
1981	11.931119311193111
1982	11.11288212873898
1983	11.565603483408763
1984	11.482055047230054
1985	10.837050448818715
1986	9.769849812906866
1987	11.078585497190147
1988	10.740414352698613
1989	11.190822983868202
1990	11.161292601926656
1991	9.837832666578652
1992	10.259831014547997
1993	10.43269599259482
1994	10.769712055074024
1995	7.920923110958727
1996	7.865470116241998
1997	9.22297801829885
1998	8.202903895025523
1999	7.495899042507679
2000	7.83908394241973
2001	8.108963281085396
2002	8.410328779025038
2003	8.7310761182594
2004	8.91081508504217
2005	8.721330066352138
2006	9.194922697174624
2007	8.832317349612968
2008	9.090772233578665
2009	9.084738258936909
2010	8.56019214975832
2011	8.51411320703718
2012	8.285099494662562
2013	8.259699275807673
2014	8.088421344672323
2015	8.482571767348885
2016	8.421838591526324
2017	8.15719376694754
2018	8.387529770064724
2019	8.284839254695903
2020	7.772124973749046
2021	7.739580299005347
2022	8.232264272880041