Year	Years
1970	1.37
1971	1.41
1972	1.45
1973	1.5
1974	1.55
1975	1.6
1976	1.65
1977	1.7
1978	1.75
1979	1.81
1980	1.86
1981	1.92
1982	1.98
1983	2.04
1984	2.1
1985	2.17
1986	2.23
1987	2.3
1988	2.37
1989	2.44
1990	2.51
1991	2.59
1992	2.67
1993	2.75
1994	2.83
1995	2.91
1996	3
1997	3.09
1998	3.18
1999	3.27
2000	3.36
2001	3.46
2002	3.56
2003	3.66
2004	3.76
2005	3.86
2006	3.97
2007	4.08
2008	4.19
2009	4.31
2010	4.42
2011	4.54
2012	4.66
2013	4.78
2014	4.91
2015	5.03