Year	Years
1970	1.2
1971	1.2
1972	1.3
1973	1.4
1974	1.5
1975	1.6
1976	1.8
1977	1.9
1978	2
1979	2.1
1980	2.3
1981	2.4
1982	2.6
1983	2.7
1984	2.9
1985	3.1
1986	3.2
1987	3.4
1988	3.6
1989	3.8
1990	4
1991	4.1
1992	4.3
1993	4.5
1994	4.7
1995	4.9
1996	5.1
1997	5.3
1998	5.5
1999	5.7
2000	5.9
2001	6.1
2002	6.4
2003	6.6
2004	6.8
2005	7
2006	7.2
2007	7.4
2008	7.6
2009	7.8