Year	Years
1970	1.99
1971	2.05
1972	2.11
1973	2.17
1974	2.24
1975	2.31
1976	2.38
1977	2.45
1978	2.52
1979	2.6
1980	2.68
1981	2.77
1982	2.86
1983	2.95
1984	3.04
1985	3.14
1986	3.24
1987	3.34
1988	3.45
1989	3.56
1990	3.68
1991	3.8
1992	3.92
1993	4.05
1994	4.18
1995	4.32
1996	4.45
1997	4.59
1998	4.72
1999	4.86
2000	4.99
2001	5.13
2002	5.26
2003	5.4
2004	5.53
2005	5.66
2006	5.8
2007	5.93
2008	6.06
2009	6.19
2010	6.32
2011	6.45
2012	6.58
2013	6.7
2014	6.83
2015	6.96