Year	% of expense
1988	43.02624406198895
1989	41.38425443169969
1990	38.25301204819277
1991	36.53009239677034
1992	26.710125659390144
1993	42.06265052642367
1994	33.452293106404454
1995	36.44498970391542
1996	38.05814840429127
1997	40.87085675523718
1998	38.14970841076116
1999	34.690125095625795
2000	37.165085751805435
2001	37.242977253192535
2002	38.91979816038808
2003	35.92659833078753
2004	33.34406871565769
2005	32.15205611597395
2006	28.384336211544447
2007	30.17900221463232
2008	28.72551630406712
2009	29.09792312647879
2010	31.245409107934126
2011	39.88579964538062
2012	32.50669823075518
2013	35.37358831585926
2014	32.302968341283986
2015	34.008148146702034
2016	35.53511720855172
2017	34.56589144579163
2018	35.02259156176057
2019	34.06660246601659
2020	38.00681904840172