Year	Years
1970	0.97
1971	0.99
1972	1.01
1973	1.04
1974	1.07
1975	1.09
1976	1.12
1977	1.15
1978	1.17
1979	1.2
1980	1.23
1981	1.26
1982	1.29
1983	1.32
1984	1.35
1985	1.38
1986	1.41
1987	1.44
1988	1.47
1989	1.5
1990	1.53
1991	1.56
1992	1.58
1993	1.61
1994	1.64
1995	1.67
1996	1.7
1997	1.73
1998	1.77
1999	1.8
2000	1.84
2001	1.87
2002	1.91
2003	1.95
2004	2
2005	2.04
2006	2.09
2007	2.13
2008	2.18
2009	2.23
2010	2.28
2011	2.33
2012	2.38
2013	2.44
2014	2.49
2015	2.55