Year	Years
1970	1.86
1971	1.91
1972	1.96
1973	2.01
1974	2.06
1975	2.11
1976	2.17
1977	2.22
1978	2.28
1979	2.34
1980	2.39
1981	2.45
1982	2.52
1983	2.58
1984	2.64
1985	2.71
1986	2.78
1987	2.84
1988	2.91
1989	2.98
1990	3.06
1991	3.13
1992	3.21
1993	3.28
1994	3.36
1995	3.44
1996	3.52
1997	3.6
1998	3.69
1999	3.77
2000	3.86
2001	3.95
2002	4.04
2003	4.13
2004	4.22
2005	4.31
2006	4.41
2007	4.51
2008	4.61
2009	4.71
2010	4.81
2011	4.91
2012	5.01
2013	5.12
2014	5.23
2015	5.34