Year	Years
1970	0.63
1971	0.65
1972	0.67
1973	0.69
1974	0.72
1975	0.75
1976	0.77
1977	0.8
1978	0.83
1979	0.86
1980	0.89
1981	0.92
1982	0.95
1983	0.99
1984	1.03
1985	1.06
1986	1.1
1987	1.14
1988	1.18
1989	1.23
1990	1.27
1991	1.32
1992	1.37
1993	1.42
1994	1.48
1995	1.53
1996	1.59
1997	1.66
1998	1.73
1999	1.8
2000	1.86
2001	1.94
2002	2.01
2003	2.08
2004	2.16
2005	2.24
2006	2.32
2007	2.4
2008	2.48
2009	2.57
2010	2.65
2011	2.74
2012	2.83
2013	2.92
2014	3.01
2015	3.1