Year	% of expense
1990	37.39089919803929
1991	36.53009239677034
1992	34.26124197002141
1993	31.729181410710073
1994	33.452293106404454
1995	36.44498970391542
1998	32.44415160359395
1999	30.468923191928756
2000	31.345425555552843
2001	30.74761499099865
2002	37.910946120852756
2003	34.899757232280606
2004	30.966222473074616
2005	34.443520751157735
2006	34.58889284242453
2007	35.23696603513618
2008	36.05891392441535
2009	35.683321998657455
2010	37.610344204306415
2011	36.602431525027235
2012	34.0461388552925
2013	37.10443392459204
2014	35.289594885145945
2015	36.7577506651581
2016	35.539900662204275
2017	36.438993683900556
2018	35.774061360953695
2019	35.99906124505026
2020	32.833329212469934
2021	31.728165298518398
2022	29.84944853016347