Year	Years
1970	1.6
1971	1.66
1972	1.72
1973	1.78
1974	1.85
1975	1.91
1976	1.98
1977	2.06
1978	2.13
1979	2.21
1980	2.29
1981	2.38
1982	2.47
1983	2.56
1984	2.66
1985	2.75
1986	2.86
1987	2.97
1988	3.08
1989	3.19
1990	3.31
1991	3.44
1992	3.57
1993	3.7
1994	3.84
1995	3.99
1996	4.12
1997	4.25
1998	4.39
1999	4.53
2000	4.66
2001	4.8
2002	4.94
2003	5.08
2004	5.22
2005	5.36
2006	5.5
2007	5.65
2008	5.79
2009	5.94
2010	6.08
2011	6.23
2012	6.38
2013	6.53
2014	6.68
2015	6.83