Year	Years
1970	1.68
1971	1.72
1972	1.77
1973	1.81
1974	1.86
1975	1.91
1976	1.96
1977	2.02
1978	2.07
1979	2.12
1980	2.18
1981	2.24
1982	2.3
1983	2.36
1984	2.42
1985	2.48
1986	2.55
1987	2.61
1988	2.68
1989	2.75
1990	2.82
1991	2.89
1992	2.97
1993	3.04
1994	3.12
1995	3.2
1996	3.28
1997	3.36
1998	3.45
1999	3.53
2000	3.62
2001	3.71
2002	3.8
2003	3.89
2004	3.98
2005	4.07
2006	4.16
2007	4.26
2008	4.35
2009	4.45
2010	4.55
2011	4.65
2012	4.75
2013	4.85
2014	4.96
2015	5.06