Year	% of expense
1972	7.961564859299932
1973	8.644457208500862
1974	6.848404255319148
1975	6.171735241502684
1976	7.028657616892911
1977	7.482169290808774
1978	8.430913348946136
1979	8.770900557348197
1980	9.063566899691107
1981	10.0594033553104
1982	10.315778593208952
1983	10.943474646716542
1984	12.675260462652304
1985	13.071062313508502
1986	13.110995556395954
1987	13.401360544217686
1988	13.58823626274103
1989	15.071858147217437
1990	14.257263213798597
1991	15.48773806838323
1992	15.119329396987071
1993	15.565475978235291
1994	16.777311820314168
1995	18.251233648770043
1996	17.587077073988812
1997	19.422137544738884
1998	19.747660594796738
1999	18.912123816391276
2000	18.106004908627714
2001	16.801677207942074
2002	14.558337005840837
2003	12.569194114071555
2004	11.5613262515453
2005	10.859359052867932
2006	9.850315674256516
2007	8.673096750264289
2008	7.697607380460603
2009	7.312272359262033
2010	7.680190970196045
2011	7.90376276286169
2012	8.703871088643398
2013	8.73775533731754
2014	9.179413341109406
2015	9.09896509990054
2016	10.21501968007158
2017	10.563451928444245
2018	10.562564040785324
2019	11.041411159621022
2020	11.429757261214641
2021	12.923886928239964
2022	14.135856781627961