Year	Years
1970	0.75
1971	0.77
1972	0.79
1973	0.82
1974	0.84
1975	0.86
1976	0.89
1977	0.91
1978	0.94
1979	0.96
1980	0.99
1981	1.02
1982	1.05
1983	1.07
1984	1.1
1985	1.14
1986	1.17
1987	1.2
1988	1.23
1989	1.27
1990	1.3
1991	1.34
1992	1.38
1993	1.41
1994	1.45
1995	1.49
1996	1.54
1997	1.58
1998	1.62
1999	1.67
2000	1.71
2001	1.76
2002	1.81
2003	1.86
2004	1.91
2005	1.96
2006	2.01
2007	2.06
2008	2.12
2009	2.17
2010	2.23
2011	2.29
2012	2.35
2013	2.41
2014	2.47
2015	2.53