Year	Years
1970	1.33
1971	1.37
1972	1.41
1973	1.45
1974	1.49
1975	1.53
1976	1.57
1977	1.62
1978	1.66
1979	1.71
1980	1.76
1981	1.81
1982	1.86
1983	1.91
1984	1.97
1985	2.02
1986	2.08
1987	2.14
1988	2.2
1989	2.26
1990	2.33
1991	2.4
1992	2.46
1993	2.53
1994	2.61
1995	2.68
1996	2.75
1997	2.83
1998	2.9
1999	2.98
2000	3.05
2001	3.13
2002	3.21
2003	3.29
2004	3.37
2005	3.45
2006	3.53
2007	3.62
2008	3.7
2009	3.79
2010	3.88
2011	3.97
2012	4.06
2013	4.16
2014	4.25
2015	4.35