Year	Years
1970	1.29
1971	1.33
1972	1.37
1973	1.41
1974	1.45
1975	1.5
1976	1.54
1977	1.59
1978	1.64
1979	1.69
1980	1.74
1981	1.79
1982	1.85
1983	1.9
1984	1.96
1985	2.02
1986	2.08
1987	2.14
1988	2.2
1989	2.26
1990	2.33
1991	2.39
1992	2.46
1993	2.53
1994	2.6
1995	2.67
1996	2.75
1997	2.83
1998	2.91
1999	2.99
2000	3.07
2001	3.16
2002	3.25
2003	3.34
2004	3.43
2005	3.53
2006	3.62
2007	3.72
2008	3.83
2009	3.93
2010	4.04
2011	4.14
2012	4.25
2013	4.37
2014	4.48
2015	4.6