Year	Percent
1971	7.248
1972	7.675
1973	8.277
1974	9.139
1975	9.488
1976	9.221
1977	9.112
1978	8.868
1979	8.788
1980	8.527
1981	9.317
1982	9.606
1983	9.66
1984	10.19
1985	10.66
1986	10.51
1987	10.33
1988	10.36
1989	10.66
1990	10.32
1991	10.21
1992	10.09
1993	10.08
1994	9.974
1995	10.1
1996	10.29
1997	10.16
1998	10.77
1999	10.68
2000	10.38
2001	9.609
2002	9.38
2003	9.158
2004	8.919
2005	9.303
2006	9.101
2007	8.615
2008	8.837
2009	8.922
2010	8.338