Year	% of expense
1990	63.87388043399112
1991	63.74742986005173
1992	55.42199949143922
1993	54.56532560981129
1994	53.78907476982447
1995	54.906801682801444
1996	51.3164311108703
1997	51.636834108821574
1998	52.96415978980589
1999	51.052528575009184
2000	51.0130443116511
2001	48.38411026975864
2002	49.07405567305918
2003	44.97904644214012
2004	39.525161990654176
2005	40.61867280941386
2006	35.35499336280334
2007	38.204680530671375
2008	39.458476179357284
2009	40.96027168137228
2010	40.4527821589275
2011	40.655572669430796
2012	52.77730339143098
2013	50.56434331183095
2014	51.94589521052626
2015	53.524059303664494
2016	53.00715055406401
2017	52.380141526927474