Year	Years
1970	0.42
1971	0.43
1972	0.45
1973	0.48
1974	0.5
1975	0.52
1976	0.54
1977	0.57
1978	0.59
1979	0.62
1980	0.65
1981	0.67
1982	0.7
1983	0.73
1984	0.76
1985	0.79
1986	0.82
1987	0.85
1988	0.89
1989	0.92
1990	0.95
1991	0.99
1992	1.02
1993	1.06
1994	1.1
1995	1.14
1996	1.17
1997	1.21
1998	1.24
1999	1.28
2000	1.31
2001	1.35
2002	1.38
2003	1.42
2004	1.46
2005	1.5
2006	1.53
2007	1.57
2008	1.61
2009	1.66
2010	1.7
2011	1.74
2012	1.79
2013	1.83
2014	1.88
2015	1.93