Year	% of expense
1990	4.224015187470337
1991	1.9553072625698324
1992	2.685284640171858
1993	3.1097203207510264
1994	3.253878168747635
1995	3.986000388878087
1996	3.9011958439521663
1997	3.960213667342052
1998	4.3290820908927605
1999	5.0725846821291505
2000	6.974343851371277
2001	7.335797554734149
2002	4.293231284381727
2003	5.68534929220854
2004	4.792732588493265
2005	5.976624500986004
2006	6.499797074341373
2007	5.0393050500107055
2008	3.419397634932581
2009	2.9363966511584247
2010	4.81149317805075
2011	4.7028748090484
2012	5.9862558459069195
2013	6.728418435660736
2014	7.395877046593863
2015	8.699357863030151
2016	11.595978756795944
2017	15.210657129975843
2018	18.504384687035433
2019	19.472824926958012
2020	18.906653108687955