Year	Years
1970	0.89
1971	0.92
1972	0.95
1973	0.99
1974	1.03
1975	1.07
1976	1.11
1977	1.16
1978	1.2
1979	1.25
1980	1.3
1981	1.36
1982	1.41
1983	1.47
1984	1.53
1985	1.6
1986	1.67
1987	1.74
1988	1.81
1989	1.89
1990	1.98
1991	2.07
1992	2.17
1993	2.27
1994	2.38
1995	2.49
1996	2.6
1997	2.71
1998	2.82
1999	2.93
2000	3.04
2001	3.16
2002	3.27
2003	3.39
2004	3.51
2005	3.63
2006	3.75
2007	3.88
2008	4
2009	4.13
2010	4.25
2011	4.38
2012	4.51
2013	4.64
2014	4.77
2015	4.9