Year	Years
1970	1.2
1971	1.3
1972	1.4
1973	1.4
1974	1.5
1975	1.6
1976	1.7
1977	1.8
1978	1.9
1979	2
1980	2.1
1981	2.2
1982	2.3
1983	2.4
1984	2.5
1985	2.7
1986	2.8
1987	2.9
1988	3
1989	3.2
1990	3.3
1991	3.4
1992	3.6
1993	3.7
1994	3.9
1995	4
1996	4.2
1997	4.3
1998	4.5
1999	4.6
2000	4.8
2001	5
2002	5.1
2003	5.3
2004	5.5
2005	5.7
2006	5.9
2007	6
2008	6.2
2009	6.4