Year	% of expense
1987	2.132312597026724
1988	3.080520306008944
1989	2.5020850708924103
1990	52.874527906000836
1991	55.85005679666792
1992	57.645369705671214
1993	64.35011709601874
1994	62.797518330513256
1995	64.36701999518189
1996	64.34226151207282
1997	65.43311449535739
1998	61.35717891396841
1999	57.426334598751275
2000	65.73014552447457
2001	54.779626464282394
2002	52.76519218571285
2003	47.39177494337057
2004	46.174661657235674
2005	47.31810920403762
2006	46.429318169896995
2007	47.577926547998835
2008	50.13113758076718
2009	47.010304787539155
2010	46.48107035830461
2011	46.834289101695525
2012	47.57341378558964
2013	47.19603368908447
2014	47.08485039440856
2015	48.55809670768787
2016	42.05521415526992
2017	46.38803441467337
2018	46.48921216774694
2019	46.43631826893865
2020	47.31202035724285