Year	Years
1970	1.51
1971	1.55
1972	1.6
1973	1.66
1974	1.71
1975	1.76
1976	1.82
1977	1.88
1978	1.94
1979	2
1980	2.06
1981	2.13
1982	2.2
1983	2.27
1984	2.34
1985	2.41
1986	2.48
1987	2.56
1988	2.64
1989	2.72
1990	2.81
1991	2.89
1992	2.98
1993	3.07
1994	3.16
1995	3.26
1996	3.36
1997	3.45
1998	3.55
1999	3.65
2000	3.76
2001	3.86
2002	3.97
2003	4.08
2004	4.19
2005	4.31
2006	4.42
2007	4.54
2008	4.66
2009	4.79
2010	4.91
2011	5.04
2012	5.17
2013	5.3
2014	5.43
2015	5.57