Year	Years
1970	0.31
1971	0.32
1972	0.33
1973	0.35
1974	0.36
1975	0.37
1976	0.39
1977	0.4
1978	0.42
1979	0.44
1980	0.45
1981	0.47
1982	0.49
1983	0.51
1984	0.54
1985	0.56
1986	0.58
1987	0.61
1988	0.63
1989	0.66
1990	0.69
1991	0.72
1992	0.76
1993	0.79
1994	0.83
1995	0.86
1996	0.9
1997	0.94
1998	0.98
1999	1.02
2000	1.06
2001	1.1
2002	1.14
2003	1.18
2004	1.23
2005	1.27
2006	1.32
2007	1.37
2008	1.41
2009	1.46
2010	1.51
2011	1.56
2012	1.62
2013	1.67
2014	1.73
2015	1.78