Year	Years
1970	1.1
1971	1.2
1972	1.3
1973	1.4
1974	1.4
1975	1.5
1976	1.6
1977	1.7
1978	1.8
1979	1.9
1980	2
1981	2.1
1982	2.2
1983	2.3
1984	2.4
1985	2.5
1986	2.6
1987	2.7
1988	2.9
1989	3
1990	3.1
1991	3.2
1992	3.4
1993	3.5
1994	3.6
1995	3.8
1996	3.9
1997	4.1
1998	4.2
1999	4.4
2000	4.5
2001	4.7
2002	4.9
2003	5
2004	5.2
2005	5.4
2006	5.5
2007	5.7
2008	5.9
2009	6.1