Year	% of expense
1981	3.204047217537943
1982	3.2494279176201375
1983	1.8797814207650274
1984	2.6370431893687707
1985	2.16796875
1986	3.7551695616211744
1987	3.6931391682930492
1988	5.477621910487642
1989	6.007067137809187
1990	5.929487179487179
1991	6.956589027315639
1992	10.056540245219491
1993	8.542551475727112
1994	12.468752693733299
1995	16.860304905125375
1996	19.259141065138145
1997	19.096242485236786
1998	15.812169939815284
1999	15.42027278073516
2000	12.9082473542069
2001	11.37823497220085
2002	9.205358067674172
2003	9.335009679662761
2004	10.198066500462376
2005	9.598672968555023
2006	8.89073109194295
2007	9.262116106410554
2008	8.834555269424873
2009	9.686040188263606
2010	9.173467002097963
2011	8.859355522619525
2012	9.84293812317711
2013	9.48164154980011
2014	8.91593731210152
2015	8.035784661757022
2016	7.263178923956122
2017	6.471137591646642
2018	6.055505843523759
2019	5.816489933236543
2020	5.352786582185224
2021	5.400628968633498
2022	6.634614398147928