Year	Years
1970	1.4
1971	1.5
1972	1.6
1973	1.7
1974	1.8
1975	1.9
1976	2
1977	2.1
1978	2.2
1979	2.3
1980	2.4
1981	2.5
1982	2.7
1983	2.8
1984	2.9
1985	3
1986	3.2
1987	3.3
1988	3.4
1989	3.6
1990	3.7
1991	3.8
1992	4
1993	4.1
1994	4.3
1995	4.4
1996	4.6
1997	4.7
1998	4.9
1999	5
2000	5.2
2001	5.4
2002	5.5
2003	5.7
2004	5.9
2005	6
2006	6.2
2007	6.4
2008	6.6
2009	6.7