Year	% of expense
1972	4.801894918173986
1973	4.333118556701027
1974	3.321083435415807
1975	3.824855119124275
1976	4.778986345753304
1977	6.661941885187785
1978	6.327956095127223
1979	7.896408157504756
1980	7.883015830426619
1981	9.303873286303746
1982	10.780845399175755
1983	12.083069301227027
1984	14.712482468443186
1985	14.440916757614849
1986	15.511445098136154
1987	14.871742253232032
1988	15.099833610648927
1989	15.776742085826267
1990	15.131980368749149
1991	15.922086545910632
1992	15.567333905355621
1993	16.920693670464974
1994	17.03270470279299
1995	6.670160560293488
1996	7.683173542088134
1997	7.560975609756097
1998	8.89634188507019
1999	8.85462699270025
2000	9.74610244988864
2001	9.49244583042099
2002	8.481037726507576
2003	8.297244712232473
2004	8.047368314874216
2005	8.077750629079903
2006	7.776425620897108
2007	7.577333610715485
2008	6.8870602815927136
2009	5.525369775801981
2010	4.614796355629392
2011	4.9721189591078065
2012	7.81112036910373
2013	7.543834378723795
2014	6.690870761843415
2015	7.844849528882909
2016	7.207306289749509
2017	6.994083876119587
2018	6.016256550948665
2019	5.936486280185737
2020	4.862929600462091
2021	4.314245427952102
2022	3.926658548572395