Year	% of expense
1978	15.26391069573279
1979	14.916873426425653
1980	13.461538461538458
1981	13.617906781227454
1982	13.3075236954801
1983	12.8957528957529
1984	12.451715708767509
1985	12.511704355024737
1986	11.433356386726842
1987	11.731405682172431
1988	12.84245235864421
1989	12.736911506601498
1990	12.401212925234532
1991	10.190603806606857
1992	11.779487612612769
1993	11.484753743351002
1994	11.301799656446148
1995	14.65095144716387
1996	14.283435517702628
1997	14.650822723277566
1998	16.18185952234456
1999	14.929144608972068
2000	15.015205467345332
2001	14.699472407715605
2002	14.932159817737144
2003	15.173859270413143
2004	15.223532307656875
2005	15.848510553908902
2006	15.91425045013616
2007	16.070970874614563
2008	15.51911939103039
2009	14.935699988741495
2010	14.133475395222352
2011	13.901507355570361
2012	13.709371109438633
2013	14.543648199605922
2014	14.422785126710519
2015	14.182085039041633
2016	14.799684091967427
2017	15.14433059485124
2018	15.66184261738988
2019	16.099574564081788
2020	15.24104726047473
2021	15.317730861659081
2022	15.079781017271147