Year	Years
1970	0.6
1971	0.7
1972	0.7
1973	0.8
1974	0.8
1975	0.9
1976	0.9
1977	1
1978	1.1
1979	1.1
1980	1.2
1981	1.3
1982	1.4
1983	1.5
1984	1.6
1985	1.7
1986	1.8
1987	1.9
1988	2
1989	2.1
1990	2.2
1991	2.3
1992	2.4
1993	2.5
1994	2.7
1995	2.8
1996	3
1997	3.1
1998	3.2
1999	3.4
2000	3.6
2001	3.7
2002	3.9
2003	4
2004	4.2
2005	4.4
2006	4.6
2007	4.8
2008	4.9
2009	5.1