Year	Years
1970	1.25
1971	1.29
1972	1.33
1973	1.38
1974	1.42
1975	1.47
1976	1.51
1977	1.56
1978	1.61
1979	1.67
1980	1.72
1981	1.77
1982	1.83
1983	1.89
1984	1.95
1985	2.01
1986	2.07
1987	2.14
1988	2.21
1989	2.28
1990	2.35
1991	2.42
1992	2.5
1993	2.58
1994	2.66
1995	2.74
1996	2.82
1997	2.91
1998	2.99
1999	3.08
2000	3.17
2001	3.26
2002	3.36
2003	3.46
2004	3.56
2005	3.66
2006	3.76
2007	3.87
2008	3.97
2009	4.08
2010	4.2
2011	4.31
2012	4.43
2013	4.55
2014	4.67
2015	4.79