Year	% of expense
1975	3.080920564216778
1976	3.409478349812479
1977	4.850746268656716
1978	8.091853471842537
1979	9.403623040911867
1981	6.642908054169637
1982	4.955820207452939
1983	8.939936356404136
1984	9.40548653381139
1985	9.522383590357839
1986	10.09404792579232
1987	12.146583370902299
1988	12.259530421610703
1989	14.733377849852141
1990	16.276351673087746
1991	19.136264523057896
1992	18.079700454667023
1993	27.490586116568434
1994	30.693087557603686
1995	26.021786492374726
1996	25.93377440592698
1997	23.986156162215014
2002	19.665065282244004
2003	20.7925477377687
2004	21.085985333220943
2005	20.20896473635322
2006	17.20105424812186
2007	17.56030515065303
2008	15.08533053760095
2009	13.95858150127702
2010	17.86158371043323
2011	19.079808236955838
2012	19.439790368873357
2013	22.589766659266445
2014	22.722171151727288
2015	24.23321602598809