Year	Years
1970	5
1971	5.1
1972	5.2
1973	5.4
1974	5.5
1975	5.6
1976	5.8
1977	5.9
1978	6
1979	6.2
1980	6.3
1981	6.5
1982	6.6
1983	6.7
1984	6.9
1985	7
1986	7.2
1987	7.3
1988	7.5
1989	7.6
1990	7.8
1991	7.9
1992	8.1
1993	8.2
1994	8.3
1995	8.5
1996	8.6
1997	8.7
1998	8.9
1999	9
2000	9.1
2001	9.3
2002	9.4
2003	9.5
2004	9.7
2005	9.8
2006	9.9
2007	10
2008	10.1
2009	10.2