Year	Years
1970	1.63
1971	1.68
1972	1.73
1973	1.78
1974	1.83
1975	1.89
1976	1.95
1977	2.01
1978	2.07
1979	2.13
1980	2.19
1981	2.26
1982	2.33
1983	2.39
1984	2.47
1985	2.54
1986	2.61
1987	2.69
1988	2.77
1989	2.84
1990	2.93
1991	3.01
1992	3.1
1993	3.18
1994	3.27
1995	3.36
1996	3.46
1997	3.55
1998	3.65
1999	3.75
2000	3.86
2001	3.96
2002	4.07
2003	4.18
2004	4.29
2005	4.41
2006	4.52
2007	4.64
2008	4.77
2009	4.89
2010	5.02
2011	5.15
2012	5.28
2013	5.41
2014	5.55
2015	5.69