Year	Years
1970	1.31
1971	1.36
1972	1.41
1973	1.46
1974	1.51
1975	1.57
1976	1.63
1977	1.69
1978	1.75
1979	1.81
1980	1.88
1981	1.95
1982	2.02
1983	2.1
1984	2.18
1985	2.26
1986	2.34
1987	2.43
1988	2.53
1989	2.62
1990	2.72
1991	2.83
1992	2.94
1993	3.05
1994	3.17
1995	3.29
1996	3.43
1997	3.56
1998	3.69
1999	3.82
2000	3.96
2001	4.09
2002	4.23
2003	4.36
2004	4.5
2005	4.64
2006	4.77
2007	4.91
2008	5.05
2009	5.19
2010	5.34
2011	5.48
2012	5.62
2013	5.77
2014	5.91
2015	6.06