Year	Years
1970	0.53
1971	0.55
1972	0.57
1973	0.59
1974	0.61
1975	0.64
1976	0.66
1977	0.69
1978	0.72
1979	0.75
1980	0.78
1981	0.81
1982	0.84
1983	0.88
1984	0.92
1985	0.95
1986	0.99
1987	1.04
1988	1.08
1989	1.13
1990	1.18
1991	1.23
1992	1.28
1993	1.34
1994	1.4
1995	1.46
1996	1.52
1997	1.58
1998	1.64
1999	1.7
2000	1.77
2001	1.83
2002	1.9
2003	1.96
2004	2.03
2005	2.1
2006	2.17
2007	2.24
2008	2.31
2009	2.38
2010	2.46
2011	2.53
2012	2.61
2013	2.69
2014	2.77
2015	2.85