Year	% of expense
1972	2.5718608169440245
1973	3.36
1974	3.172978505629478
1975	3.358464701850582
1976	4.459203036053131
1977	5.207100591715976
1978	5.553931598947677
1979	6.003791868548556
1980	7.27821566325675
1981	7.671492355567581
1982	7.151475265986619
1983	7.122861586314152
1984	7.959505897650228
1985	8.11075716736094
1986	8.31500219973603
1987	7.362202168408752
1988	6.491031390134529
1989	3.7451115711985277
1990	4.745609746925883
1991	3.89549436795995
1992	4.0140693803028675
1993	2.911869981619425
1994	3.7252666720951058
1995	3.406978783096616
1996	3.019773055752022
1997	3.192105970001555
1998	4.141813076678753
1999	6.700890841606549
2000	6.868201244852395
2001	6.233838240378679
2002	5.650229013393413
2003	4.554024368432623
2004	5.58448993428754
2005	5.916403350055477
2006	6.512766525406012
2007	6.8461691869786625
2008	6.7902301133435925
2009	4.951012413806454
2010	5.741902953274917
2011	5.782613179067707
2012	5.6833704957589735
2013	5.626528337667667
2014	5.673203356892378
2015	5.330723930836588
2016	4.800891769612712
2017	4.413342031529457
2018	4.063575427517882
2019	3.762292484764687
2020	3.6556386084129824
2021	3.302508993891266
2022	3.46452687677858