Year	% of expense
1987	9.323865680279024
1988	10.936900264641118
1989	21.718751392341897
1991	11.296257206845834
1992	9.470862874893616
1993	8.010858850367537
1994	6.327659852549837
1995	7.201328686594567
1996	2.3851346270601046
1997	3.5462161018590512
1998	6.55802286707831
1999	4.796772261222205
2000	7.801888268810678
2001	6.172952829756895
2002	7.583051567468265
2003	7.567549379185033
2004	4.970583558594371
2005	3.2961502977438566
2006	7.053588779365677
2007	6.231610773972139
2008	1.752866302784849
2009	1.6428167717752382
2010	1.353318228831853
2011	1.8189410800724337
2012	2.0158059498602516
2013	1.9456118811012537
2014	1.72191381527093
2015	2.31975157656247
2016	1.956171848316909
2017	2.696140205357012
2018	3.3787625646949473
2019	3.703784127089882
2020	3.7186029977769595
2021	3.252655547616946
2022	3.9938168439387995