Year	Years
1970	1.61
1971	1.66
1972	1.72
1973	1.77
1974	1.83
1975	1.89
1976	1.95
1977	2.01
1978	2.07
1979	2.14
1980	2.2
1981	2.27
1982	2.34
1983	2.42
1984	2.49
1985	2.57
1986	2.65
1987	2.73
1988	2.81
1989	2.9
1990	2.99
1991	3.08
1992	3.18
1993	3.27
1994	3.37
1995	3.47
1996	3.58
1997	3.69
1998	3.81
1999	3.92
2000	4.04
2001	4.16
2002	4.28
2003	4.4
2004	4.52
2005	4.65
2006	4.78
2007	4.91
2008	5.04
2009	5.17
2010	5.31
2011	5.44
2012	5.58
2013	5.72
2014	5.86
2015	6.01