Year	Years
1970	0.7
1971	0.72
1972	0.74
1973	0.76
1974	0.78
1975	0.81
1976	0.83
1977	0.85
1978	0.87
1979	0.9
1980	0.92
1981	0.95
1982	0.97
1983	1
1984	1.03
1985	1.05
1986	1.08
1987	1.11
1988	1.14
1989	1.17
1990	1.2
1991	1.24
1992	1.27
1993	1.3
1994	1.34
1995	1.37
1996	1.41
1997	1.45
1998	1.49
1999	1.52
2000	1.56
2001	1.61
2002	1.65
2003	1.69
2004	1.73
2005	1.78
2006	1.83
2007	1.87
2008	1.92
2009	1.97
2010	2.02
2011	2.07
2012	2.13
2013	2.18
2014	2.23
2015	2.29