Year	Years
1970	1.2
1971	1.3
1972	1.4
1973	1.5
1974	1.6
1975	1.7
1976	1.9
1977	2
1978	2.1
1979	2.3
1980	2.4
1981	2.6
1982	2.7
1983	2.9
1984	3.1
1985	3.3
1986	3.5
1987	3.6
1988	3.8
1989	4
1990	4.2
1991	4.4
1992	4.6
1993	4.8
1994	5.1
1995	5.3
1996	5.5
1997	5.7
1998	5.9
1999	6.2
2000	6.4
2001	6.7
2002	6.9
2003	7.1
2004	7.4
2005	7.6
2006	7.9
2007	8.1
2008	8.3
2009	8.6