Year	% of expense
1981	7.130811852565647
1982	7.345537757437071
1983	7.540983606557377
1984	7.5789036544850505
1985	8.28125
1986	7.6923076923076925
1987	6.5906020117099535
1988	8.403473613894455
1989	7.917402826855123
1990	6.561085972850679
1991	8.666718254275322
1992	8.665269042627532
1993	8.687704962098811
1994	8.516507197655375
1995	10.086428626492362
1996	10.180467565393412
1997	10.529860305047151
1998	10.694549744709098
1999	11.314590131263609
2000	12.459259486043072
2001	12.960402627924445
2002	13.72225608411578
2003	14.38668107780518
2004	13.949723966766165
2005	13.843599127101685
2006	13.12372124517161
2007	13.0624893943409
2008	12.732404425969133
2009	12.152839513165633
2010	11.958984600990947
2011	11.303951491693311
2012	13.240959141723291
2013	16.00552538975174
2014	16.932137452718333
2015	17.682800729252097
2016	18.46698019829382
2017	19.328300606479644
2018	19.87258831984453
2019	20.205200244512287
2020	19.271719169475123
2021	19.353243200187286
2022	19.034609730592507