Year	Years
1970	0.57
1971	0.59
1972	0.61
1973	0.64
1974	0.66
1975	0.69
1976	0.71
1977	0.74
1978	0.77
1979	0.8
1980	0.83
1981	0.86
1982	0.89
1983	0.93
1984	0.97
1985	1.01
1986	1.05
1987	1.09
1988	1.13
1989	1.18
1990	1.23
1991	1.28
1992	1.33
1993	1.39
1994	1.45
1995	1.51
1996	1.58
1997	1.65
1998	1.71
1999	1.78
2000	1.85
2001	1.93
2002	2
2003	2.07
2004	2.15
2005	2.22
2006	2.3
2007	2.38
2008	2.46
2009	2.54
2010	2.63
2011	2.71
2012	2.8
2013	2.89
2014	2.98
2015	3.07