Year	Years
1970	0.5
1971	0.6
1972	0.6
1973	0.6
1974	0.7
1975	0.7
1976	0.8
1977	0.8
1978	0.9
1979	0.9
1980	1
1981	1
1982	1.1
1983	1.2
1984	1.3
1985	1.4
1986	1.5
1987	1.6
1988	1.7
1989	1.8
1990	1.9
1991	2.1
1992	2.2
1993	2.3
1994	2.5
1995	2.6
1996	2.7
1997	2.9
1998	3
1999	3.2
2000	3.4
2001	3.5
2002	3.7
2003	3.9
2004	4
2005	4.2
2006	4.4
2007	4.6
2008	4.8
2009	5