Year	Years
1970	0.65
1971	0.67
1972	0.69
1973	0.71
1974	0.73
1975	0.75
1976	0.77
1977	0.8
1978	0.82
1979	0.85
1980	0.87
1981	0.9
1982	0.92
1983	0.95
1984	0.98
1985	1.01
1986	1.04
1987	1.07
1988	1.11
1989	1.14
1990	1.18
1991	1.21
1992	1.25
1993	1.29
1994	1.33
1995	1.37
1996	1.42
1997	1.47
1998	1.52
1999	1.57
2000	1.62
2001	1.67
2002	1.72
2003	1.77
2004	1.83
2005	1.88
2006	1.94
2007	1.99
2008	2.05
2009	2.11
2010	2.17
2011	2.23
2012	2.29
2013	2.35
2014	2.41
2015	2.47