Year	% of expense
1972	24.659606656580937
1973	28.96
1974	32.54861821903787
1975	31.871144619602465
1976	31.261859582542694
1977	34.12228796844182
1978	37.7667348728442
1979	28.502211923319994
1980	32.03085695119906
1981	32.40427547016642
1982	29.768564220686628
1983	30.502851218247795
1984	27.91864028977431
1985	28.80829861961938
1986	28.81654201495821
1987	28.630786210478476
1988	27.387892376681616
1989	25.19438693351737
1990	23.47986312187418
1991	23.225907384230286
1992	22.390183653742884
1993	21.348070039663344
1994	19.25738946339875
1995	15.577766088023848
1996	15.386389495371935
1997	15.629727016978384
1998	14.244892691072438
1999	11.063322323662545
2000	13.517636452556244
2001	11.978312791607356
2002	12.232378998544087
2003	10.133628439366827
2004	10.04328163999175
2005	9.744912582401835
2006	9.785150156894739
2007	6.499709612938689
2008	6.834644442345206
2009	10.845436383652078
2010	11.09575003572128
2011	10.91197992493088
2012	12.035439141477495
2013	13.166244323317233
2014	13.352694500144006
2015	14.761985549663434
2016	14.803154739924027
2017	13.898154272559369
2018	11.600188218365377
2019	10.927548899024933
2020	10.88481014829188
2021	12.02789914296641
2022	10.88089731525372