Year	% of expense
1975	19.45063103192279
1976	21.820661438799863
1977	22.732491389207805
1978	24.71295790049207
1979	20.21168328923265
1981	20.926585887384178
1982	19.323857087975412
1983	22.235481304693717
1984	22.154590177603602
1985	23.98562659080701
1986	22.526410718886886
1987	24.016229793263346
1988	23.34763948497854
1989	25.269483926356962
1990	26.557291892125885
1991	23.425651706967813
1992	17.42753101405147
1993	20.260314341846758
1994	20.667281105990785
1995	22.03050108932462
1996	22.726022743816625
1997	23.85889218257725
2002	29.848707915229937
2003	29.927352711785687
2004	28.836236292998414
2005	28.484836157272746
2006	23.35053848875291
2007	24.141145907707855
2008	23.400048736734416
2009	24.553808127126644
2010	24.80473988578741
2011	24.335951622982282
2012	25.903555528729576
2013	24.21442175598959
2014	25.788159713774515
2015	27.197211694639954