Year	% of expense
1990	0.9823000648688722
1991	3.132551687102837
1992	2.5868627948262746
1993	2.460691823899371
1994	6.205019655276685
1995	3.7554893745898745
1996	24.7744993120318
1997	10.219733865091843
1998	1.7644859813084113
1999	2.6435091588556023
2000	2.2289713455697875
2001	2.243575615991537
2002	7.441339374794907
2003	14.745968218460167
2004	4.80702589213401
2005	8.669473898449342
2006	7.84630457271861
2007	8.543036116634187
2008	16.34855665312559
2009	17.767599563162875
2010	9.531447094072327
2011	8.357452838124258
2012	11.892279803532688
2013	11.600958375313096
2014	15.703975389666724
2015	19.064451418933327
2016	22.262260932042533
2017	22.83736039368168
2018	24.625536725719364
2019	22.232483755762473
2020	22.87070773705555