Year	% of expense
1980	2.06065034709536
1981	2.4461997259611508
1982	2.73972602739726
1983	2.9844392943290927
1984	2.737164229853791
1985	2.031682468641423
1986	6.497302158273381
1987	6.567642347458862
1988	7.322362546243142
1989	7.431946745007345
1990	13.574075368803747
1991	21.127634918883125
1992	18.60662775469849
1993	21.130510701306594
1994	20.893390915723327
1995	22.41092241092241
1996	21.56363280101891
1997	16.084503346017584
1998	15.758561948590172
1999	21.06676960335884
2000	20.00057523539711
2001	15.989386132103098
2002	17.340507016431893
2003	17.354925106636244
2004	17.421699772779814
2005	18.776644045469475
2006	18.812980787650677
2007	19.382599050396202
2008	20.754130415617514
2009	19.174073727456427
2010	17.45580361298141
2011	13.666436977915374
2012	14.20585443703769
2013	15.099303829078584
2014	14.435539509476344
2015	14.048392237438243
2016	16.87573363917085
2017	17.908147256086476
2018	23.40642158255325
2019	24.031606785938994
2020	22.267822473313874
2021	20.8631012051291
2022	18.9708557119012