Year	Years
1970	1.9
1971	1.96
1972	2.02
1973	2.08
1974	2.14
1975	2.2
1976	2.27
1977	2.33
1978	2.4
1979	2.47
1980	2.54
1981	2.62
1982	2.69
1983	2.77
1984	2.85
1985	2.93
1986	3.01
1987	3.09
1988	3.18
1989	3.27
1990	3.36
1991	3.45
1992	3.54
1993	3.63
1994	3.73
1995	3.83
1996	3.93
1997	4.03
1998	4.13
1999	4.24
2000	4.35
2001	4.46
2002	4.57
2003	4.69
2004	4.81
2005	4.93
2006	5.06
2007	5.18
2008	5.31
2009	5.45
2010	5.58
2011	5.72
2012	5.86
2013	6
2014	6.14
2015	6.29