Year	Years
1970	1.98
1971	2.05
1972	2.13
1973	2.21
1974	2.29
1975	2.37
1976	2.46
1977	2.56
1978	2.66
1979	2.76
1980	2.87
1981	2.98
1982	3.1
1983	3.23
1984	3.36
1985	3.5
1986	3.65
1987	3.81
1988	3.97
1989	4.14
1990	4.32
1991	4.51
1992	4.7
1993	4.9
1994	5.11
1995	5.32
1996	5.47
1997	5.62
1998	5.77
1999	5.91
2000	6.06
2001	6.21
2002	6.35
2003	6.49
2004	6.64
2005	6.78
2006	6.92
2007	7.06
2008	7.2
2009	7.34
2010	7.49
2011	7.63
2012	7.77
2013	7.91
2014	8.05
2015	8.19