Year	% of expense
1998	12.592762187188825
1999	10.74234561932176
2000	12.693484904105393
2001	11.52739843619796
2002	12.602583149923426
2003	14.335392539029334
2004	12.427885724860435
2005	10.759957540499688
2006	10.460283225493638
2007	9.535541855811893
2008	9.753786779319777
2009	9.0514782027188
2010	8.081682435348927
2011	8.334920006982284
2012	7.758968323070238
2013	8.1275941692901
2014	7.647713640626324
2015	8.475240981904372
2016	10.60985978199165
2017	10.117953914455558
2018	11.35028441764322
2019	11.474547749263778
2020	9.420935748973028
2021	10.705945703319578