Year	% of expense
1972	22.60934025203855
1973	25.39175856065003
1974	33.652636671504595
1975	38.32016632016632
1976	36.82645330312256
1977	31.941912365625196
1978	30.087615733548752
1979	9.832090683154512
1980	14.80840008659883
1981	18.73827713985086
1982	19.771909744931328
1983	19.74453344879844
1984	19.501789652554322
1985	19.092947059837904
1986	15.634514130162255
1987	15.822513473787359
1988	17.386652067884338
1989	16.188750397923453
1990	16.5715413884701
1991	18.065333708814418
1992	14.935390163277573
1993	15.049869766850899
1994	19.560611643330876
1995	20.706331096958756
1996	15.984839512021793
1997	15.80346339237895
1998	17.934985676921162
1999	15.387916757039097
2000	17.933098587413987
2001	14.19898275437509
2002	12.892125779196705
2003	11.939444339527457
2004	12.06279341331707
2005	10.973597093327903
2006	10.31613267346022
2007	9.833221784108694
2008	9.90951223559231
2009	10.725106279576345