Year	Years
1970	0.48
1971	0.5
1972	0.51
1973	0.53
1974	0.55
1975	0.57
1976	0.59
1977	0.61
1978	0.63
1979	0.65
1980	0.67
1981	0.69
1982	0.72
1983	0.74
1984	0.77
1985	0.79
1986	0.82
1987	0.85
1988	0.88
1989	0.91
1990	0.94
1991	0.97
1992	1
1993	1.04
1994	1.07
1995	1.11
1996	1.15
1997	1.19
1998	1.23
1999	1.27
2000	1.32
2001	1.36
2002	1.41
2003	1.45
2004	1.5
2005	1.55
2006	1.6
2007	1.66
2008	1.71
2009	1.77
2010	1.82
2011	1.88
2012	1.94
2013	2
2014	2.07
2015	2.13