Year	Years
1970	1.27
1971	1.3
1972	1.34
1973	1.37
1974	1.41
1975	1.45
1976	1.49
1977	1.53
1978	1.57
1979	1.61
1980	1.65
1981	1.69
1982	1.74
1983	1.78
1984	1.83
1985	1.87
1986	1.92
1987	1.97
1988	2.02
1989	2.07
1990	2.12
1991	2.17
1992	2.23
1993	2.28
1994	2.33
1995	2.39
1996	2.44
1997	2.5
1998	2.56
1999	2.62
2000	2.68
2001	2.74
2002	2.8
2003	2.86
2004	2.92
2005	2.99
2006	3.06
2007	3.13
2008	3.19
2009	3.27
2010	3.34
2011	3.41
2012	3.49
2013	3.56
2014	3.64
2015	3.72