Year	Years
1970	0.88
1971	0.91
1972	0.93
1973	0.96
1974	0.98
1975	1.01
1976	1.03
1977	1.06
1978	1.09
1979	1.12
1980	1.15
1981	1.18
1982	1.21
1983	1.24
1984	1.28
1985	1.31
1986	1.34
1987	1.38
1988	1.42
1989	1.46
1990	1.49
1991	1.53
1992	1.58
1993	1.62
1994	1.66
1995	1.71
1996	1.76
1997	1.81
1998	1.86
1999	1.91
2000	1.96
2001	2.02
2002	2.07
2003	2.13
2004	2.19
2005	2.25
2006	2.31
2007	2.37
2008	2.43
2009	2.5
2010	2.56
2011	2.63
2012	2.7
2013	2.77
2014	2.84
2015	2.91