Year	% of expense
1987	10.639531139305726
1988	16.132289825801564
1989	12.272250310025756
1991	10.697432225729814
1992	9.196206307733453
1993	7.897429600523903
1994	6.300460829493088
1995	6.342483660130719
1996	6.591824519969588
1997	6.796206912606893
2002	23.751501297896247
2003	23.800092890380586
2004	25.525866098590793
2005	26.69690620995464
2006	42.52168679699498
2007	39.41785574363537
2008	45.76405880938574
2009	44.74596428678527
2010	41.570288184918034
2011	41.62265996140653
2012	41.378878290315804
2013	42.79728450743722
2014	41.70329148468346
2015	37.212696264212234