Year	% of expense
1972	57.85986010553439
1973	53.24029822213738
1974	52.4756053487532
1975	54.68034438541858
1976	49.05377808032669
1977	49.3145623175554
1978	36.19553277187843
1979	36.247271283985015
1980	33.90435403283377
1981	33.45882889820603
1982	24.940204038464667
1983	30.18823588650456
1984	29.89611479994556
1985	29.854861214332644
1986	27.809793618893085
1987	25.836439750787832
1988	26.037185918758805
1989	24.22368453140632
1990	21.965454448482657
1995	21.38661713037373
1996	20.01637838056169
1997	21.99069634673292
1998	21.58169205265235
1999	22.031411647539617
2000	22.007498057851784
2001	21.97202911737125
2002	23.23708192383263
2003	22.58413541427521
2004	23.265602014645083
2005	23.494318425262325
2006	22.82630297888645
2007	22.17508560908342
2008	21.47208196222161
2009	22.376523743792877
2010	21.52529039970597
2011	20.39837010600958
2012	20.163309121154185
2013	17.377877120796935
2014	21.865195241958972
2015	20.570150389619155
2016	21.74043502657374
2017	21.92958131940383
2018	21.42634510764135
2019	21.40898574438408
2020	19.377002136099335
2021	18.663207000773
2022	18.16772025089046