Year	Years
1970	0.48
1971	0.49
1972	0.51
1973	0.53
1974	0.55
1975	0.57
1976	0.59
1977	0.61
1978	0.64
1979	0.66
1980	0.69
1981	0.71
1982	0.74
1983	0.77
1984	0.8
1985	0.83
1986	0.86
1987	0.9
1988	0.94
1989	0.98
1990	1.02
1991	1.07
1992	1.11
1993	1.17
1994	1.22
1995	1.28
1996	1.34
1997	1.39
1998	1.45
1999	1.51
2000	1.57
2001	1.63
2002	1.69
2003	1.76
2004	1.82
2005	1.89
2006	1.95
2007	2.02
2008	2.09
2009	2.16
2010	2.24
2011	2.31
2012	2.39
2013	2.47
2014	2.55
2015	2.63