Year	% of expense
1980	8.713920350748996
1981	10.018537922140727
1982	11.57685493280325
1983	14.501253369909664
1984	13.583815028901732
1985	30.82562864377834
1986	27.21166816546763
1987	29.354885685160916
1988	21.526980482204365
1989	22.580241897677908
1990	12.3820177585122
1991	16.43996247654784
1992	14.882093267304406
1993	13.587930001218618
1994	15.265002500501112
1995	14.342800057085773
1996	14.107965121975116
1997	20.257184096575255
1998	16.65861534158806
1999	23.652525209795204
2000	22.367668894505425
2001	17.547816348233507
2002	16.331140074696044
2003	16.403630592203157
2004	11.478538480661847
2005	14.294051079417086
2006	12.540572796966535
2007	12.644200294404401
2008	12.268366898615717
2009	11.227147804551493
2010	9.41957629217268
2011	9.326612626185387
2012	9.747635614632234
2013	9.87271427691859
2014	10.686905098050262
2015	10.372675622844586
2016	10.433565283134836
2017	9.512505593036643
2018	8.89728109265597
2019	9.706690800886737
2020	8.576617512982747
2021	9.45854522403112
2022	8.794942074583377