Year	Years
1970	0.56
1971	0.57
1972	0.59
1973	0.61
1974	0.63
1975	0.65
1976	0.67
1977	0.69
1978	0.71
1979	0.73
1980	0.75
1981	0.78
1982	0.8
1983	0.83
1984	0.85
1985	0.88
1986	0.91
1987	0.93
1988	0.96
1989	1
1990	1.03
1991	1.06
1992	1.1
1993	1.13
1994	1.17
1995	1.21
1996	1.25
1997	1.29
1998	1.32
1999	1.36
2000	1.41
2001	1.45
2002	1.49
2003	1.53
2004	1.58
2005	1.62
2006	1.67
2007	1.71
2008	1.76
2009	1.81
2010	1.86
2011	1.91
2012	1.96
2013	2.01
2014	2.06
2015	2.12