Year	% of expense
1973	18.945513291232132
1974	18.028462943103094
1975	15.276061650517
1976	14.773314331522228
1977	15.692509663773599
1978	12.896069926828456
1979	12.910816199057074
1980	12.650808753567999
1986	10.191629325960555
1987	10.52384901764999
1988	13.240512963230048
1989	12.68938673221563
1990	13.194077942279382
1991	12.920020249895433
1992	11.86618137004042
1993	11.43912765865119
1994	11.281034065070521
1995	12.628799624520193
1996	13.464939054700823
1997	13.929766847147057
1998	14.084447570985692
1999	14.028981202214396
2000	14.478455649260038
2001	14.594540531526423
2002	14.932159817737144
2003	15.484411870601464
2004	15.352164257868125
2005	15.487145022691992
2006	15.039804626845775
2007	15.149777553230104
2008	14.53754332872917
2009	14.23418740844657
2010	14.35883323312106
2011	14.13303636198372
2012	13.586582474943446
2013	13.633851410062034
2014	13.482400019195632
2015	13.186538377101552
2016	13.363662529344344
2017	13.367993547829512
2018	13.71603581019149
2019	13.53612783190201
2020	12.231064897797522
2021	11.551162564335447
2022	11.539297282093571