Year	Years
1970	0.44
1971	0.46
1972	0.48
1973	0.49
1974	0.51
1975	0.53
1976	0.55
1977	0.56
1978	0.58
1979	0.61
1980	0.63
1981	0.65
1982	0.67
1983	0.7
1984	0.72
1985	0.75
1986	0.77
1987	0.8
1988	0.83
1989	0.86
1990	0.89
1991	0.92
1992	0.96
1993	0.99
1994	1.03
1995	1.06
1996	1.1
1997	1.14
1998	1.18
1999	1.22
2000	1.27
2001	1.31
2002	1.36
2003	1.4
2004	1.45
2005	1.5
2006	1.55
2007	1.6
2008	1.65
2009	1.7
2010	1.76
2011	1.82
2012	1.87
2013	1.93
2014	1.99
2015	2.06