Year	% of expense
1990	61.87577934801981
1991	63.121440145340266
1992	64.69758872527962
1993	63.60184431787361
1994	62.90455323976241
1995	46.80295236606958
1996	48.28426856636236
1997	47.33137902777908
1998	46.43462133598423
1999	49.19322482811814
2000	47.6195284297205
2001	47.012135077472145
2002	48.12031472263571
2003	48.04098546378393
2004	47.87941676693931
2005	46.93486019100369
2006	47.29422089425583
2007	48.570955786760535
2008	48.70410852041668
2009	49.283185028793866
2010	50.657184965662566
2011	49.78929398870042
2012	50.90539399984655
2013	51.667483225790754
2014	50.94303348780205
2015	50.900526677769676
2016	51.12714981280304
2017	51.011999306099796
2018	50.263677461443876
2019	50.28694267718472
2020	51.3369208203391
2021	51.58871668660235
2022	51.628348850465514