Year	Years
1970	0.42
1971	0.44
1972	0.46
1973	0.48
1974	0.5
1975	0.52
1976	0.54
1977	0.56
1978	0.59
1979	0.61
1980	0.64
1981	0.67
1982	0.7
1983	0.73
1984	0.76
1985	0.8
1986	0.83
1987	0.87
1988	0.91
1989	0.96
1990	1
1991	1.05
1992	1.1
1993	1.15
1994	1.21
1995	1.27
1996	1.34
1997	1.41
1998	1.48
1999	1.55
2000	1.62
2001	1.7
2002	1.78
2003	1.85
2004	1.93
2005	2.01
2006	2.09
2007	2.17
2008	2.26
2009	2.34
2010	2.42
2011	2.5
2012	2.58
2013	2.66
2014	2.74
2015	2.82