Year	Years
1970	1.62
1971	1.66
1972	1.7
1973	1.75
1974	1.79
1975	1.84
1976	1.88
1977	1.93
1978	1.98
1979	2.03
1980	2.09
1981	2.14
1982	2.19
1983	2.25
1984	2.3
1985	2.36
1986	2.42
1987	2.48
1988	2.54
1989	2.61
1990	2.67
1991	2.74
1992	2.8
1993	2.87
1994	2.94
1995	3.01
1996	3.09
1997	3.16
1998	3.24
1999	3.32
2000	3.4
2001	3.48
2002	3.56
2003	3.64
2004	3.73
2005	3.81
2006	3.9
2007	3.99
2008	4.08
2009	4.18
2010	4.27
2011	4.37
2012	4.46
2013	4.56
2014	4.66
2015	4.76