Year	Years
1970	1.31
1971	1.35
1972	1.39
1973	1.43
1974	1.47
1975	1.51
1976	1.56
1977	1.6
1978	1.65
1979	1.7
1980	1.75
1981	1.8
1982	1.86
1983	1.91
1984	1.97
1985	2.03
1986	2.09
1987	2.16
1988	2.22
1989	2.29
1990	2.36
1991	2.44
1992	2.51
1993	2.59
1994	2.67
1995	2.76
1996	2.85
1997	2.95
1998	3.04
1999	3.14
2000	3.24
2001	3.34
2002	3.44
2003	3.55
2004	3.65
2005	3.76
2006	3.86
2007	3.97
2008	4.08
2009	4.18
2010	4.29
2011	4.39
2012	4.5
2013	4.6
2014	4.71
2015	4.81