Year	Years
1970	1.62
1971	1.66
1972	1.7
1973	1.75
1974	1.79
1975	1.84
1976	1.89
1977	1.94
1978	1.99
1979	2.04
1980	2.09
1981	2.15
1982	2.2
1983	2.26
1984	2.32
1985	2.38
1986	2.44
1987	2.5
1988	2.56
1989	2.63
1990	2.69
1991	2.76
1992	2.83
1993	2.9
1994	2.97
1995	3.04
1996	3.12
1997	3.19
1998	3.27
1999	3.35
2000	3.43
2001	3.51
2002	3.59
2003	3.68
2004	3.76
2005	3.85
2006	3.94
2007	4.03
2008	4.12
2009	4.21
2010	4.3
2011	4.4
2012	4.5
2013	4.59
2014	4.69
2015	4.79