Year	Percent
1971	54.61
1972	54.82
1973	21.74
1974	18.83
1975	23.57
1976	18.74
1977	18.72
1978	19.82
1979	16.57
1980	19.33
1981	17.4
1982	19.85
1983	20.36
1984	20.81
1985	24.3
1986	26.44
1987	22.2
1988	19.13
1989	20.49
1990	21.96
1991	20.58
1992	23.48
1993	21.08
1994	24.74
1995	25.21
1996	20.66
1997	20.24
1998	24.82
1999	22.23
2000	23.82
2001	21.2
2002	25.07
2003	26.42
2004	23.57
2005	8.857
2006	24.08
2007	24.49