Year	Years
1970	0.81
1971	0.84
1972	0.87
1973	0.9
1974	0.94
1975	0.97
1976	1.01
1977	1.05
1978	1.09
1979	1.14
1980	1.18
1981	1.23
1982	1.28
1983	1.33
1984	1.39
1985	1.44
1986	1.5
1987	1.57
1988	1.63
1989	1.7
1990	1.78
1991	1.86
1992	1.94
1993	2.03
1994	2.12
1995	2.21
1996	2.3
1997	2.39
1998	2.48
1999	2.57
2000	2.67
2001	2.76
2002	2.86
2003	2.96
2004	3.06
2005	3.16
2006	3.26
2007	3.37
2008	3.48
2009	3.58
2010	3.69
2011	3.8
2012	3.92
2013	4.03
2014	4.14
2015	4.26