Year	Years
1970	0.5
1971	0.6
1972	0.6
1973	0.7
1974	0.7
1975	0.8
1976	0.8
1977	0.9
1978	0.9
1979	1
1980	1.1
1981	1.2
1982	1.2
1983	1.3
1984	1.4
1985	1.5
1986	1.6
1987	1.7
1988	1.8
1989	2
1990	2.1
1991	2.2
1992	2.3
1993	2.4
1994	2.6
1995	2.7
1996	2.9
1997	3
1998	3.1
1999	3.3
2000	3.5
2001	3.6
2002	3.8
2003	4
2004	4.1
2005	4.3
2006	4.5
2007	4.7
2008	4.8
2009	5