Year	% of expense
1972	46.77804295942721
1973	44.561261625556
1974	45.169946332737034
1975	35.73866406630912
1976	37.54638725169177
1977	35.902287975227935
1978	34.11991688928465
1979	28.490338164251206
1980	34.967285208623835
1981	31.883530482256596
1982	33.042648862242814
1983	33.19575809687589
1984	31.894424016521434
1985	32.03718559765939
1986	32.643112701252235
1987	32.07928291882338
1988	31.484138972809667
1989	31.075553810411964
1990	31.365336089745536
1991	32.890018353804884
1992	34.5644488999103
1993	34.76269275967096
1994	36.27139281607252
1995	36.710482804232804
1996	36.88900537282139
1997	40.23802088754728
1998	40.93833866847738
1999	40.277307085918046
2000	39.76319148358363
2001	40.37039386059491
2002	40.7014469415303
2003	41.44482455065132
2004	39.69812602389419
2005	38.96088477309881
2006	38.86498321906517
2007	37.81052212158828
2008	34.9093581577658
2009	34.94441286663366
2010	34.64520178459346
2011	34.84539227252949
2012	35.05276531957788