Year	% of expense
1972	17.611622492484816
1973	18.36746743849493
1974	16.697426989469115
1975	15.513841839941186
1976	15.585654330408241
1977	15.692509663773599
1978	15.739858341491761
1979	15.145963549615631
1980	13.935323421152294
1981	13.788273922371477
1982	13.442575406032464
1983	13.02448844798687
1984	12.828614604688328
1985	12.66124661246609
1986	12.76401569254262
1987	13.273808726055773
1988	14.131518209226368
1989	13.811824246606855
1990	13.194077942279382
1991	11.233919184823998
1992	11.86618137004042
1993	11.43912765865119
1994	11.266449409669846
1995	13.841140124376526
1996	13.919806161318245
1997	14.097642799854682
1998	14.084447570985692
1999	13.060246569750642
2000	12.9089400418315
2001	13.036318455812951
2002	14.223004107345698
2003	14.38668107780518
2004	13.887243935114459
2005	14.082973790188156
2006	13.773804119460594
2007	13.68251650383336
2008	14.44759057258883
2009	14.154602091742902
2010	14.071040944433962
2011	13.683780235028923
2012	13.382650067778046
2013	13.169031320237641
2014	13.305263514464778
2015	13.152218486046195
2016	13.403016125561816
2017	13.715868118943995
2018	13.863977246327906
2019	13.889826371878845
2020	12.507354894804743
2021	12.692276740152785
2022	12.385276041337445