Year	Years
1970	0.94
1971	0.97
1972	1
1973	1.03
1974	1.06
1975	1.09
1976	1.12
1977	1.15
1978	1.18
1979	1.22
1980	1.25
1981	1.28
1982	1.32
1983	1.35
1984	1.38
1985	1.41
1986	1.44
1987	1.48
1988	1.51
1989	1.53
1990	1.56
1991	1.59
1992	1.61
1993	1.64
1994	1.66
1995	1.68
1996	1.7
1997	1.72
1998	1.74
1999	1.77
2000	1.79
2001	1.82
2002	1.86
2003	1.89
2004	1.93
2005	1.96
2006	2
2007	2.04
2008	2.09
2009	2.13
2010	2.18
2011	2.22
2012	2.27
2013	2.33
2014	2.38
2015	2.43