Year	% of expense
1972	42.57425742574257
1973	38.04347826086957
1974	28.10810810810811
1977	26.99696663296259
1978	29.09090909090909
1979	29.364368845120858
1980	32.73972602739726
1981	28.537735849056606
1982	29.451697127937337
1983	30.63396575659417
1984	33.643486777668954
1985	33.5032437442076
1986	39.22349427575909
1987	43.02203567681007
1988	37.80113885238721
1989	36.986301369863014
1990	37.76470588235294
1991	6.140750873993008
1992	20.72558139534884
1993	26.55466399197593
1994	28.98701298701299
1995	31.014338821030268
1996	30.363036303630363
1997	36.78520625889047
1998	37.965732934457435
2001	35.16648764769065
2002	35.604166666666664
2003	33.85271749211649
2004	31.396666127205048
2005	31.589118477776125
2006	24.226652263576547