Year	Years
1970	0.78
1971	0.81
1972	0.83
1973	0.86
1974	0.89
1975	0.92
1976	0.95
1977	0.98
1978	1.02
1979	1.05
1980	1.09
1981	1.13
1982	1.16
1983	1.2
1984	1.24
1985	1.29
1986	1.33
1987	1.37
1988	1.42
1989	1.47
1990	1.52
1991	1.57
1992	1.62
1993	1.67
1994	1.73
1995	1.79
1996	1.85
1997	1.91
1998	1.97
1999	2.03
2000	2.1
2001	2.17
2002	2.24
2003	2.31
2004	2.38
2005	2.45
2006	2.53
2007	2.6
2008	2.68
2009	2.76
2010	2.84
2011	2.92
2012	3.01
2013	3.1
2014	3.19
2015	3.28