Year	Years
1970	1.29
1971	1.34
1972	1.38
1973	1.42
1974	1.47
1975	1.52
1976	1.57
1977	1.62
1978	1.67
1979	1.72
1980	1.78
1981	1.84
1982	1.89
1983	1.95
1984	2.02
1985	2.08
1986	2.15
1987	2.21
1988	2.28
1989	2.36
1990	2.43
1991	2.51
1992	2.58
1993	2.66
1994	2.75
1995	2.83
1996	2.92
1997	3.01
1998	3.09
1999	3.19
2000	3.28
2001	3.37
2002	3.47
2003	3.57
2004	3.67
2005	3.78
2006	3.88
2007	3.99
2008	4.1
2009	4.21
2010	4.33
2011	4.44
2012	4.56
2013	4.68
2014	4.81
2015	4.93