Year	Years
1970	0.6
1971	0.62
1972	0.64
1973	0.66
1974	0.68
1975	0.69
1976	0.71
1977	0.73
1978	0.76
1979	0.78
1980	0.8
1981	0.82
1982	0.85
1983	0.87
1984	0.9
1985	0.92
1986	0.95
1987	0.97
1988	1
1989	1.03
1990	1.06
1991	1.09
1992	1.12
1993	1.16
1994	1.19
1995	1.23
1996	1.26
1997	1.3
1998	1.34
1999	1.38
2000	1.42
2001	1.46
2002	1.5
2003	1.54
2004	1.59
2005	1.63
2006	1.68
2007	1.72
2008	1.77
2009	1.82
2010	1.87
2011	1.92
2012	1.97
2013	2.02
2014	2.07
2015	2.13