Year	Years
1970	1.69
1971	1.74
1972	1.8
1973	1.85
1974	1.91
1975	1.97
1976	2.03
1977	2.1
1978	2.16
1979	2.23
1980	2.3
1981	2.37
1982	2.45
1983	2.52
1984	2.6
1985	2.68
1986	2.76
1987	2.84
1988	2.93
1989	3.02
1990	3.11
1991	3.2
1992	3.3
1993	3.4
1994	3.5
1995	3.6
1996	3.71
1997	3.82
1998	3.93
1999	4.04
2000	4.16
2001	4.28
2002	4.39
2003	4.51
2004	4.64
2005	4.76
2006	4.89
2007	5.02
2008	5.15
2009	5.28
2010	5.41
2011	5.55
2012	5.69
2013	5.83
2014	5.97
2015	6.11