Year	Years
1970	0.8
1971	0.9
1972	0.9
1973	1
1974	1
1975	1
1976	1.1
1977	1.1
1978	1.2
1979	1.2
1980	1.3
1981	1.3
1982	1.4
1983	1.4
1984	1.5
1985	1.6
1986	1.6
1987	1.7
1988	1.7
1989	1.8
1990	1.8
1991	1.9
1992	2
1993	2
1994	2.1
1995	2.1
1996	2.2
1997	2.3
1998	2.3
1999	2.4
2000	2.5
2001	2.6
2002	2.6
2003	2.7
2004	2.8
2005	2.8
2006	2.9
2007	3
2008	3.1
2009	3.2