Year	% of expense
1972	18.329466357308586
1973	17.604355716878402
1974	15.10673234811166
1975	14.176663031624864
1976	13.201035375323556
1977	13.733650416171225
1978	9.960629921259843
1979	10.920976735243222
1980	13.279530447542188
1981	16.072434607645874
1983	15.062671703296704
1984	14.399771884801824
1985	12.96674843281548
1986	16.65544750146804
1987	13.498262682418346
1988	12.52203923922422
1989	12.014525343024724
1990	11.686911916115973
1991	9.298032960839922
1992	9.854573658442
1993	7.836627836627836
1994	8.080429535769508
1995	8.080540444505647
1996	8.004279017084604
1997	9.335969028734253
1998	8.553364886784252
2008	9.148272855075394
2009	9.084738258936909
2010	10.595177723499498
2011	10.17652295826573
2012	11.15497223430681
2013	11.4598113121484
2014	11.30466659084806
2015	11.486486075058405
2016	11.299780527617928
2017	11.048165264645517
2018	9.62226310223515
2019	8.812191913198665
2020	8.714219542621514
2021	8.929581099442837
2022	9.416277503642712