Year	Years
1970	0.93
1971	0.97
1972	1
1973	1.03
1974	1.06
1975	1.1
1976	1.14
1977	1.17
1978	1.21
1979	1.25
1980	1.29
1981	1.34
1982	1.38
1983	1.43
1984	1.47
1985	1.52
1986	1.57
1987	1.62
1988	1.68
1989	1.73
1990	1.79
1991	1.84
1992	1.9
1993	1.96
1994	2.03
1995	2.09
1996	2.16
1997	2.23
1998	2.3
1999	2.37
2000	2.44
2001	2.51
2002	2.59
2003	2.67
2004	2.75
2005	2.83
2006	2.92
2007	3
2008	3.09
2009	3.18
2010	3.27
2011	3.37
2012	3.46
2013	3.56
2014	3.66
2015	3.77