Year	Percent
1960	27.79959
1961	22.38277
1962	21.5634
1963	21.17077
1964	19.20809
1965	17.04
1966	22.98976
1967	19.15312
1968	20.51823
1969	21.69024
1970	21.47137
1971	22.77631
1972	24.16388
1973	26.27297
1974	34.40673
1975	34.63151
1976	34.96502
1977	41.45847
1978	31.83837
1979	36.71141
1980	36.13012
1981	33.61639
1982	25.41864
1983	27.19579
1984	24.47138
1985	25.41348
1986	22.6827
1987	29.50306
1988	26.50757
1989	29.63319
1990	27.95087
1991	32.07399
1992	37.63152
1993	40.90392
1994	45.39252
1995	37.93686
1996	38.0882
1997	33.80224
1998	30.89567
1999	31.99164
2000	28.58195
2001	29.23513
2002	30.54187
2003	28.56857
2004	39.8119
2005	41.62466
2006	38.7233
2007	37.83303