Year	Years
1970	0.52
1971	0.53
1972	0.55
1973	0.57
1974	0.58
1975	0.6
1976	0.62
1977	0.64
1978	0.66
1979	0.68
1980	0.7
1981	0.72
1982	0.74
1983	0.76
1984	0.79
1985	0.81
1986	0.83
1987	0.86
1988	0.89
1989	0.92
1990	0.94
1991	0.97
1992	1.01
1993	1.04
1994	1.07
1995	1.11
1996	1.15
1997	1.19
1998	1.23
1999	1.27
2000	1.31
2001	1.35
2002	1.4
2003	1.44
2004	1.49
2005	1.53
2006	1.58
2007	1.63
2008	1.67
2009	1.72
2010	1.77
2011	1.82
2012	1.88
2013	1.93
2014	1.98
2015	2.03