Year	Years
1970	0.77
1971	0.8
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	1.17
1983	1.21
1984	1.25
1985	1.29
1986	1.34
1987	1.39
1988	1.44
1989	1.49
1990	1.54
1991	1.59
1992	1.65
1993	1.71
1994	1.77
1995	1.83
1996	1.9
1997	1.97
1998	2.04
1999	2.11
2000	2.18
2001	2.26
2002	2.34
2003	2.41
2004	2.49
2005	2.58
2006	2.66
2007	2.74
2008	2.83
2009	2.92
2010	3.01
2011	3.1
2012	3.19
2013	3.28
2014	3.38
2015	3.48