Year	Years
1970	1.95
1971	2.02
1972	2.1
1973	2.17
1974	2.25
1975	2.34
1976	2.42
1977	2.52
1978	2.61
1979	2.71
1980	2.81
1981	2.92
1982	3.03
1983	3.15
1984	3.27
1985	3.4
1986	3.54
1987	3.68
1988	3.82
1989	3.97
1990	4.13
1991	4.3
1992	4.48
1993	4.66
1994	4.85
1995	5.05
1996	5.22
1997	5.39
1998	5.55
1999	5.72
2000	5.88
2001	6.05
2002	6.22
2003	6.38
2004	6.55
2005	6.72
2006	6.88
2007	7.05
2008	7.22
2009	7.38
2010	7.55
2011	7.72
2012	7.88
2013	8.05
2014	8.22
2015	8.39