Year	Years
1970	1.56
1971	1.6
1972	1.65
1973	1.69
1974	1.74
1975	1.78
1976	1.83
1977	1.88
1978	1.93
1979	1.99
1980	2.04
1981	2.1
1982	2.15
1983	2.21
1984	2.27
1985	2.34
1986	2.4
1987	2.46
1988	2.53
1989	2.6
1990	2.67
1991	2.75
1992	2.82
1993	2.9
1994	2.98
1995	3.06
1996	3.15
1997	3.24
1998	3.34
1999	3.43
2000	3.52
2001	3.62
2002	3.71
2003	3.81
2004	3.91
2005	4.01
2006	4.11
2007	4.21
2008	4.31
2009	4.42
2010	4.52
2011	4.63
2012	4.73
2013	4.84
2014	4.95
2015	5.06