Year	Years
1970	1.5
1971	1.55
1972	1.6
1973	1.66
1974	1.71
1975	1.77
1976	1.83
1977	1.9
1978	1.96
1979	2.03
1980	2.1
1981	2.18
1982	2.25
1983	2.33
1984	2.41
1985	2.5
1986	2.59
1987	2.68
1988	2.77
1989	2.87
1990	2.97
1991	3.08
1992	3.19
1993	3.3
1994	3.42
1995	3.55
1996	3.67
1997	3.8
1998	3.92
1999	4.05
2000	4.19
2001	4.32
2002	4.46
2003	4.6
2004	4.74
2005	4.88
2006	5.02
2007	5.17
2008	5.31
2009	5.46
2010	5.61
2011	5.76
2012	5.91
2013	6.06
2014	6.21
2015	6.37