Year	Years
1970	0.43
1971	0.44
1972	0.45
1973	0.47
1974	0.48
1975	0.49
1976	0.51
1977	0.52
1978	0.53
1979	0.55
1980	0.56
1981	0.58
1982	0.6
1983	0.61
1984	0.63
1985	0.65
1986	0.66
1987	0.68
1988	0.7
1989	0.72
1990	0.74
1991	0.76
1992	0.78
1993	0.8
1994	0.82
1995	0.85
1996	0.87
1997	0.89
1998	0.92
1999	0.94
2000	0.97
2001	1
2002	1.02
2003	1.05
2004	1.08
2005	1.11
2006	1.14
2007	1.17
2008	1.2
2009	1.23
2010	1.26
2011	1.3
2012	1.33
2013	1.37
2014	1.4
2015	1.44