Year	% of expense
1991	7.523302263648468
1993	12.309013651568575
1994	15.466741054446786
1995	16.673103269807545
1996	17.47051837347218
1997	15.371878599408074
1998	21.2270352970413
1999	18.96055555613545
2000	17.241055545470132
2001	18.222583903686836
2002	18.859863401458433
2003	18.83136431345893
2004	19.01122587491347
2005	18.762928865345867
2006	19.110931095998104
2007	16.992164195999024
2008	16.646265253061788
2009	15.637212569036421
2010	14.174622567306077
2011	13.317068143388058
2012	15.214151246205112
2013	15.69132490549269
2014	15.965212870255682
2015	16.059609722660547
2016	16.28182824470018
2017	16.555751264541062
2018	16.36976438766138
2019	16.598991029382816
2020	15.070637141253297
2021	15.317730861659081
2022	15.079781017271147