Year	% of expense
1990	25.142884415754875
1991	23.20660172795398
1992	21.693813915963457
1993	21.030740062204423
1994	21.492827749008434
1995	23.904809804364337
1996	23.768678661954603
1997	23.673299268176503
1998	23.320403904125474
1999	22.110734463276835
2000	21.971703473981258
2001	19.692370910653082
2002	17.30597930259347
2003	15.697545974319773
2004	14.659295392953931
2005	12.813510089548942
2006	12.76488039178753
2007	11.93206658819573
2008	10.825638163333075
2009	9.350844860292579
2010	8.894200528368348
2011	9.116602194679087
2012	8.53971338504941
2013	8.397000587697732
2014	7.705896015941126
2015	7.012501288413117
2016	6.360173795282699
2017	5.871677447770461
2018	6.28625779980977
2019	6.164908435926634
2020	3.6775913132430804
2021	4.403511170471954
2022	6.046187166217299