Year	Years
1970	1.66
1971	1.71
1972	1.76
1973	1.81
1974	1.86
1975	1.92
1976	1.97
1977	2.03
1978	2.08
1979	2.14
1980	2.2
1981	2.26
1982	2.32
1983	2.38
1984	2.44
1985	2.51
1986	2.57
1987	2.63
1988	2.7
1989	2.76
1990	2.83
1991	2.9
1992	2.97
1993	3.03
1994	3.1
1995	3.17
1996	3.25
1997	3.33
1998	3.41
1999	3.5
2000	3.59
2001	3.68
2002	3.77
2003	3.86
2004	3.96
2005	4.06
2006	4.16
2007	4.27
2008	4.37
2009	4.48
2010	4.59
2011	4.71
2012	4.82
2013	4.94
2014	5.06
2015	5.19