Year	Years
1970	0.49
1971	0.51
1972	0.53
1973	0.54
1974	0.56
1975	0.58
1976	0.6
1977	0.62
1978	0.64
1979	0.66
1980	0.68
1981	0.71
1982	0.73
1983	0.75
1984	0.78
1985	0.8
1986	0.83
1987	0.86
1988	0.89
1989	0.91
1990	0.94
1991	0.98
1992	1.01
1993	1.04
1994	1.07
1995	1.11
1996	1.14
1997	1.18
1998	1.22
1999	1.26
2000	1.3
2001	1.34
2002	1.38
2003	1.43
2004	1.47
2005	1.52
2006	1.57
2007	1.62
2008	1.67
2009	1.72
2010	1.78
2011	1.83
2012	1.89
2013	1.95
2014	2.01
2015	2.07