Year	% of expense
1985	31.181556195965417
1986	31.53900458877515
1987	32.02918801428349
1988	31.269079808111645
1989	28.280098280098283
1993	31.93008990841106
1994	30.696474634565778
1995	31.630942930228457
1996	30.51453443183585
1997	30.79084141031044
1998	29.846800433839483
1999	31.83416745570134
2000	36.32763513959475
2005	43.9211062075924
2006	39.86294148655772
2007	36.42652937113903
2008	37.344050654430994
2009	29.610446576759763
2010	25.7909559741067
2011	28.945602690935907
2012	29.138315220265167
2013	30.87500867277472
2014	33.04412896824228
2015	22.619627054326777
2016	32.311677143329646
2017	28.93120998189645
2018	33.434893189003766
2019	35.019844935997156
2020	28.214210382267535