Year	Years
1970	0.97
1971	1
1972	1.03
1973	1.07
1974	1.1
1975	1.14
1976	1.18
1977	1.22
1978	1.26
1979	1.3
1980	1.34
1981	1.39
1982	1.43
1983	1.48
1984	1.53
1985	1.58
1986	1.63
1987	1.68
1988	1.74
1989	1.8
1990	1.85
1991	1.91
1992	1.98
1993	2.04
1994	2.11
1995	2.18
1996	2.25
1997	2.32
1998	2.4
1999	2.47
2000	2.55
2001	2.63
2002	2.71
2003	2.8
2004	2.88
2005	2.97
2006	3.06
2007	3.15
2008	3.24
2009	3.34
2010	3.43
2011	3.53
2012	3.63
2013	3.74
2014	3.84
2015	3.95