Year	Years
1970	0.56
1971	0.58
1972	0.6
1973	0.62
1974	0.64
1975	0.66
1976	0.69
1977	0.71
1978	0.73
1979	0.76
1980	0.78
1981	0.81
1982	0.84
1983	0.87
1984	0.9
1985	0.93
1986	0.96
1987	0.99
1988	1.03
1989	1.06
1990	1.1
1991	1.13
1992	1.17
1993	1.21
1994	1.25
1995	1.3
1996	1.34
1997	1.39
1998	1.43
1999	1.48
2000	1.53
2001	1.58
2002	1.64
2003	1.69
2004	1.74
2005	1.8
2006	1.86
2007	1.92
2008	1.98
2009	2.04
2010	2.11
2011	2.17
2012	2.24
2013	2.31
2014	2.38
2015	2.45