Year	% of expense
1972	1.493506493506494
1973	1.2445730824891466
1974	1.3814095059704978
1975	2.156334231805936
1976	1.921165948989731
1977	2.0527005386519215
1978	2.1682242990654172
1979	2.3403796376186383
1980	2.1747177493984755
1981	3.1759458628114503
1982	3.179360218906773
1983	4.131612308401512
1984	4.226387357589103
1985	4.544791007736841
1986	4.626824566235211
1987	4.416354810033143
1988	4.334701377237927
1989	4.674444269273217
1990	5.182598357915054
1991	5.309242529534399
1992	5.767046376529376
1993	6.056630255690492
1994	6.386485372888348
1995	6.361387787756205
1996	6.5702229830306536
1997	6.552300807549526
1998	6.621476674486619
1999	6.221403884428703
2000	6.181053909689001
2001	6.148271171956945
2002	6.048284121208647
2003	5.7582656664441
2004	5.7279490160652555
2005	5.673814061652903
2006	5.43606953230751
2007	5.567449349328833
2008	5.771981815151409
2009	4.9240268723593905
2010	4.982028935686048
2011	5.43384689570771
2012	5.196574138879687
2013	4.594327714183071
2014	4.3570569179151715
2015	4.0515756759497705
2016	3.790720022734411
2017	3.576838009868901
2018	3.581890258134204
2019	3.0477059587041557
2020	2.3731502220959158
2021	2.724053326004487
2022	3.8088168201606853