Year	Years
1970	0.9
1971	0.9
1972	1
1973	1.1
1974	1.1
1975	1.2
1976	1.2
1977	1.3
1978	1.4
1979	1.4
1980	1.5
1981	1.6
1982	1.7
1983	1.8
1984	1.9
1985	2
1986	2
1987	2.1
1988	2.2
1989	2.3
1990	2.5
1991	2.6
1992	2.7
1993	2.8
1994	2.9
1995	3
1996	3.1
1997	3.3
1998	3.4
1999	3.5
2000	3.7
2001	3.8
2002	3.9
2003	4.1
2004	4.2
2005	4.4
2006	4.5
2007	4.7
2008	4.8
2009	5