Year	Years
1970	1.74
1971	1.8
1972	1.86
1973	1.93
1974	1.99
1975	2.06
1976	2.13
1977	2.2
1978	2.28
1979	2.35
1980	2.43
1981	2.51
1982	2.6
1983	2.69
1984	2.78
1985	2.87
1986	2.97
1987	3.07
1988	3.17
1989	3.28
1990	3.39
1991	3.5
1992	3.62
1993	3.74
1994	3.87
1995	4
1996	4.13
1997	4.26
1998	4.39
1999	4.52
2000	4.65
2001	4.79
2002	4.93
2003	5.06
2004	5.2
2005	5.34
2006	5.49
2007	5.63
2008	5.77
2009	5.92
2010	6.07
2011	6.22
2012	6.37
2013	6.52
2014	6.67
2015	6.83