Year	Years
1970	0.52
1971	0.53
1972	0.54
1973	0.56
1974	0.58
1975	0.59
1976	0.61
1977	0.62
1978	0.64
1979	0.66
1980	0.68
1981	0.7
1982	0.72
1983	0.74
1984	0.76
1985	0.78
1986	0.8
1987	0.82
1988	0.85
1989	0.87
1990	0.89
1991	0.92
1992	0.94
1993	0.97
1994	1
1995	1.02
1996	1.05
1997	1.08
1998	1.11
1999	1.14
2000	1.17
2001	1.2
2002	1.24
2003	1.27
2004	1.3
2005	1.34
2006	1.37
2007	1.41
2008	1.45
2009	1.49
2010	1.53
2011	1.57
2012	1.61
2013	1.65
2014	1.7
2015	1.74