Year	Years
1970	1.86
1971	1.91
1972	1.96
1973	2.01
1974	2.06
1975	2.12
1976	2.18
1977	2.23
1978	2.29
1979	2.35
1980	2.42
1981	2.48
1982	2.55
1983	2.61
1984	2.68
1985	2.75
1986	2.82
1987	2.9
1988	2.98
1989	3.05
1990	3.13
1991	3.22
1992	3.3
1993	3.39
1994	3.47
1995	3.56
1996	3.66
1997	3.76
1998	3.86
1999	3.96
2000	4.06
2001	4.17
2002	4.27
2003	4.38
2004	4.48
2005	4.59
2006	4.7
2007	4.81
2008	4.92
2009	5.04
2010	5.15
2011	5.27
2012	5.38
2013	5.5
2014	5.62
2015	5.74