Year	Years
1970	1.96
1971	2.02
1972	2.08
1973	2.14
1974	2.21
1975	2.27
1976	2.34
1977	2.41
1978	2.48
1979	2.55
1980	2.63
1981	2.71
1982	2.79
1983	2.87
1984	2.96
1985	3.05
1986	3.14
1987	3.23
1988	3.33
1989	3.43
1990	3.54
1991	3.64
1992	3.75
1993	3.87
1994	3.99
1995	4.11
1996	4.22
1997	4.34
1998	4.45
1999	4.57
2000	4.68
2001	4.8
2002	4.91
2003	5.03
2004	5.15
2005	5.26
2006	5.38
2007	5.5
2008	5.62
2009	5.74
2010	5.86
2011	5.98
2012	6.1
2013	6.22
2014	6.35
2015	6.47