Year	Years
1970	1.93
1971	1.98
1972	2.03
1973	2.08
1974	2.13
1975	2.19
1976	2.24
1977	2.3
1978	2.36
1979	2.42
1980	2.48
1981	2.54
1982	2.6
1983	2.67
1984	2.74
1985	2.81
1986	2.88
1987	2.95
1988	3.02
1989	3.1
1990	3.17
1991	3.25
1992	3.33
1993	3.42
1994	3.5
1995	3.59
1996	3.68
1997	3.77
1998	3.87
1999	3.96
2000	4.06
2001	4.16
2002	4.26
2003	4.36
2004	4.46
2005	4.56
2006	4.67
2007	4.78
2008	4.89
2009	5
2010	5.11
2011	5.22
2012	5.34
2013	5.45
2014	5.57
2015	5.69