Year	% of expense
1972	25.147058823529413
1973	25.06255212677231
1974	25.312835180550593
1975	23.58859698155394
1976	23.26633165829146
1977	21.832993890020365
1978	21.743437345220407
1979	22.073101085094233
1980	23.22128518826464
1981	21.867645674479903
1982	19.94500161759948
1983	18.82205143363878
1984	17.178546133539374
1985	17.846083266429634
1986	17.99677642182823
1987	17.221434435405627
1988	17.344636879639065
2001	25.397005193263777
2002	27.34119455748515
2003	24.196614283456615
2004	25.378249573622984
2005	25.623654534302837
2006	25.84839952578542
2007	24.979468929646867
2008	26.53843665070532
2009	24.42884658150746
2010	24.178849366265936
2011	20.519369834982935
2012	23.774283168364395
2013	23.99821019023284
2014	24.16427369866049
2015	24.469201580299423
2016	24.35166180997175
2017	24.287942660880304
2018	24.35710850400028
2019	24.727878481983634
2020	21.892892561485105
2021	23.101888659427917
2022	21.61471030781577