Year	Years
1970	0.61
1971	0.64
1972	0.66
1973	0.68
1974	0.71
1975	0.73
1976	0.76
1977	0.79
1978	0.82
1979	0.84
1980	0.88
1981	0.91
1982	0.94
1983	0.98
1984	1.01
1985	1.05
1986	1.09
1987	1.14
1988	1.18
1989	1.23
1990	1.28
1991	1.33
1992	1.39
1993	1.45
1994	1.51
1995	1.58
1996	1.65
1997	1.73
1998	1.8
1999	1.88
2000	1.95
2001	2.03
2002	2.11
2003	2.19
2004	2.27
2005	2.35
2006	2.44
2007	2.53
2008	2.61
2009	2.7
2010	2.79
2011	2.89
2012	2.98
2013	3.08
2014	3.18
2015	3.28