Year	Years
1970	2.95
1971	3.05
1972	3.14
1973	3.24
1974	3.34
1975	3.45
1976	3.55
1977	3.66
1978	3.78
1979	3.89
1980	4.01
1981	4.13
1982	4.26
1983	4.39
1984	4.52
1985	4.65
1986	4.79
1987	4.93
1988	5.07
1989	5.21
1990	5.36
1991	5.5
1992	5.65
1993	5.8
1994	5.95
1995	6.11
1996	6.25
1997	6.39
1998	6.53
1999	6.68
2000	6.83
2001	6.98
2002	7.13
2003	7.28
2004	7.44
2005	7.59
2006	7.75
2007	7.91
2008	8.07
2009	8.23
2010	8.39
2011	8.55
2012	8.72
2013	8.88
2014	9.05
2015	9.21