Year	Years
1970	1.57
1971	1.62
1972	1.67
1973	1.72
1974	1.78
1975	1.83
1976	1.89
1977	1.95
1978	2.01
1979	2.08
1980	2.14
1981	2.21
1982	2.28
1983	2.35
1984	2.42
1985	2.5
1986	2.58
1987	2.65
1988	2.74
1989	2.82
1990	2.9
1991	2.99
1992	3.08
1993	3.17
1994	3.26
1995	3.36
1996	3.45
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	4.76
2009	4.88
2010	5
2011	5.13
2012	5.25
2013	5.38
2014	5.51
2015	5.65