Year	% of expense
1972	10.435601601130209
1973	10.623914192914873
1974	10.989429908161497
1975	9.790964616680707
1976	7.879310726214967
1977	8.44724498218348
1978	8.364773942023518
1979	9.472835064086969
1980	9.511504981234403
1981	11.80853331060057
1982	12.083612137433452
1983	14.969674198915786
1984	15.324273287310778
1985	17.09464947318061
1986	18.91368548587748
1987	19.054133583884855
1988	19.652093068774008
1989	18.97545127907227
1990	15.63577825043842
1991	12.083441678413555
1992	9.100623986635876
1993	6.814361158708966
1994	5.1514624628105565
1995	3.0726735001930705
1996	1.9563172664754678
1997	2.4657129838207643
1998	1.1226733222263725
1999	4.7769374203042805
2000	8.510504663505323
2001	7.572301115374571
2002	6.1483913231838505
2003	7.204681888950959
2004	7.900231860705182
2005	7.788070130203295
2006	8.910494211391805
2007	6.2139088080229
2008	5.423032791835255
2009	5.4857413762228
2010	6.703926541432595
2011	6.075672980265446
2012	6.071932202050762
2013	5.774064193865533
2014	5.7274083840230885
2015	5.274767631848717
2016	4.380324459036319
2017	5.0038572028011
2018	5.465464077130667
2019	5.5746146148876905
2020	4.3716289890149325
2021	5.05138928567707
2022	5.965494242940064