Year	Years
1970	1.2
1971	1.3
1972	1.3
1973	1.4
1974	1.5
1975	1.6
1976	1.6
1977	1.7
1978	1.8
1979	1.9
1980	2
1981	2.1
1982	2.2
1983	2.3
1984	2.4
1985	2.5
1986	2.6
1987	2.7
1988	2.8
1989	2.9
1990	3.1
1991	3.2
1992	3.3
1993	3.4
1994	3.6
1995	3.7
1996	3.9
1997	4
1998	4.1
1999	4.3
2000	4.4
2001	4.6
2002	4.7
2003	4.9
2004	5
2005	5.2
2006	5.3
2007	5.5
2008	5.7
2009	5.8