Year	% of expense
1972	13.161819537658465
1973	13.520322472287539
1974	13.073556402654244
1975	12.819905213270141
1976	11.34785962205939
1977	10.431740478651506
1978	9.684924222281307
1979	9.72441834199232
1980	9.707059230351232
1981	9.170323928944619
1982	8.296763062150706
1983	8.570972377454893
1984	7.920326684097653
1985	7.361625068892214
1986	7.675964807038592
1987	8.152291852530562
1988	8.708160189963012
1989	8.33839388545702
1990	8.451195127767688
1991	9.003358356380877
1992	8.632830917580495
1993	8.604292595068836
1994	9.09323908703394
1995	6.242811013711721
1996	5.951612019665022
1997	6.211086691584782
1998	6.838146069017319
1999	6.9363902545481
2000	6.687091999369925
2001	6.400358559465717
2002	6.269169848289248
2003	6.081922686493456
2004	5.8509242308876175
2005	5.664150274384336
2006	5.713178084908807
2007	5.668425231379079
2008	5.608491560740466
2009	5.800485013508052
2010	5.814667062803822
2011	6.058046817210188
2012	5.923013352768161
2013	5.863956276725991
2014	5.740082718608046
2015	5.840194992115149
2016	5.743848029362991
2017	5.222205667874526
2018	5.188592660625971
2019	5.403187760299093
2020	4.518772640686312
2021	4.812642157835715
2022	5.534974548193408