Year	% of expense
1972	10.758620689655173
1973	10.971428571428572
1974	10.516431924882589
1975	10.917615539182863
1976	12.432723358449946
1977	13.460663938153719
1978	14.14291003332098
1979	14.341906202723129
1980	14.094746716697934
1981	15.269571639586358
1982	17.154872389791155
1983	17.361647361647407
1984	18.175287356321903
1985	19.544715447154438
1986	18.688865764828357
1987	18.518518518518533
1988	18.90034364261167
1989	19.88292081750036
1990	20.994838104176495
1991	19.566353187042864
1992	17.948510362694385
1993	16.791435843689158
1994	15.546930134086118
1995	13.670740774533174
1996	12.326950776561205
1997	11.055142224587957
1998	10.63581800172102
1999	7.9309261655562775
2000	6.895048405088508
2001	4.845861481712277
2002	4.345209024405254
2003	3.9935619570813006
2004	3.610232671277679
2005	3.3080577678357606
2006	3.2109326959783977
2007	3.1301767677249286
2008	3.4354974811706267
2009	4.545520052046229
2010	4.526867510088702
2011	7.463668742210314
2012	10.302121609891689
2013	11.242483154204521
2014	10.978623072759701
2015	9.56173606048527
2016	8.80767747300883
2017	8.057228015930082
2018	6.860850900994543
2019	5.766222797555728
2020	3.983131867469636
2021	3.287828766848001
2022	3.3175120092559287