Year	Years
1970	1.35
1971	1.39
1972	1.44
1973	1.48
1974	1.53
1975	1.58
1976	1.63
1977	1.68
1978	1.74
1979	1.8
1980	1.86
1981	1.92
1982	1.98
1983	2.05
1984	2.12
1985	2.19
1986	2.26
1987	2.34
1988	2.42
1989	2.5
1990	2.58
1991	2.67
1992	2.76
1993	2.85
1994	2.94
1995	3.03
1996	3.1
1997	3.19
1998	3.27
1999	3.35
2000	3.43
2001	3.52
2002	3.6
2003	3.69
2004	3.78
2005	3.87
2006	3.96
2007	4.05
2008	4.15
2009	4.24
2010	4.34
2011	4.44
2012	4.54
2013	4.64
2014	4.74
2015	4.85