Year	Percent
1961	28.13358
1962	27.91595
1963	30.96591
1964	34.29934
1965	37.97592
1966	40.13177
1967	39.62981
1968	40.07386
1969	45.896
1970	53.93823
1971	58.23864
1972	48.24993
1973	34.82017
1974	39.84154
1975	46.16424
1976	40.78091
1977	46.26877
1978	45.41965
1979	45.58985
1980	53.32241
1981	58.74376
1982	60.49623
1983	53.45158
1984	53.14557
1985	52.44008
1986	51.35481
1987	49.67242
1988	51.92265
1989	52.7465
1990	48.94675
1991	52.15498
1992	45.70211
1993	36.94603
1994	39.76806
1995	43.70099
1996	48.39884
1997	50.05045
1998	48.81944
1999	52.88844
2000	49.24348
2001	52.2504
2002	58.0033
2003	54.0311
2004	58.91886