Year	Years
1970	1.2
1971	1.3
1972	1.3
1973	1.4
1974	1.4
1975	1.5
1976	1.5
1977	1.6
1978	1.6
1979	1.7
1980	1.7
1981	1.8
1982	1.8
1983	1.9
1984	2
1985	2
1986	2
1987	2.1
1988	2.1
1989	2.1
1990	2.1
1991	2.2
1992	2.2
1993	2.3
1994	2.3
1995	2.4
1996	2.5
1997	2.5
1998	2.6
1999	2.7
2000	2.8
2001	2.8
2002	2.9
2003	3
2004	3.1
2005	3.2
2006	3.3
2007	3.4
2008	3.5
2009	3.7