Year	Years
1970	0.6
1971	0.62
1972	0.64
1973	0.66
1974	0.68
1975	0.7
1976	0.72
1977	0.74
1978	0.77
1979	0.79
1980	0.81
1981	0.84
1982	0.86
1983	0.88
1984	0.91
1985	0.93
1986	0.96
1987	0.99
1988	1.01
1989	1.04
1990	1.07
1991	1.09
1992	1.12
1993	1.15
1994	1.18
1995	1.2
1996	1.23
1997	1.27
1998	1.3
1999	1.34
2000	1.37
2001	1.41
2002	1.45
2003	1.49
2004	1.53
2005	1.58
2006	1.62
2007	1.67
2008	1.72
2009	1.77
2010	1.82
2011	1.87
2012	1.93
2013	1.98
2014	2.04
2015	2.1