Year	Percent
1960	0.09
1961	0.12
1962	0.1
1963	0.11
1964	0.11
1965	0.13
1966	0.19
1967	0.21
1968	0.23
1969	0.38
1970	0.37
1971	0.42
1972	0.44
1973	0.46
1974	0.53
1975	0.55
1976	0.52
1977	0.56
1978	0.7
1979	0.71
1980	0.74
1981	0.73
1982	0.77
1983	0.73
1984	0.85
1985	0.8
1986	0.89
1987	0.88
1988	0.89
1989	0.93
1990	0.94
1991	0.96
1992	1.02
1993	1.03
1994	1.03
1995	0.96
1996	1.04
1997	0.97
1998	0.99
1999	1.01
2000	1.06
2001	1.03
2002	0.96
2003	0.84
2004	0.85
2005	0.81
2006	0.8
2007	0.81
2008	0.82