Year	% of expense
1972	13.534675615212526
1973	12.781323480013437
1974	11.647606946209233
1975	10.924170616113745
1976	10.393366756652526
1977	9.596883199491135
1978	9.286094123903217
1979	8.572396656878247
1980	8.274465247245962
1981	7.398119122257054
1982	7.085255616818574
1983	6.54638352227367
1984	6.58950027909163
1985	6.0021520615174655
1986	6.12627474505099
1987	6.457213126612495
1988	5.970592264486963
1989	6.15223536802429
1990	6.334268889989544
1991	6.1438166732516795
1992	5.802369617788863
1993	5.453751586186194
1994	6.075648842605083
1995	7.577776518892717
1996	8.246544034183199
1997	8.441733933679739
1998	7.8236650995372985
1999	8.047817942640293
2000	8.73976579005275
2001	9.118513275952605
2002	9.211484055264098
2003	9.549452659880929
2004	9.57506439645536
2005	9.246401668982408
2006	9.377613894423458
2007	9.314468847132368
2008	9.313795163206704
2009	8.909198238635154
2010	8.825140150447474
2011	9.033859395268689
2012	9.254210156433015
2013	9.243968605654318
2014	9.262299310273676
2015	9.187549896609477
2016	9.287598645286756
2017	9.334579010028746
2018	9.285104442727159
2019	9.44083569642214
2020	8.971022205574005
2021	9.212967518932603
2022	9.171430505777963