Year	Years
1970	1.39
1971	1.43
1972	1.46
1973	1.5
1974	1.54
1975	1.58
1976	1.63
1977	1.67
1978	1.72
1979	1.76
1980	1.81
1981	1.86
1982	1.9
1983	1.96
1984	2.01
1985	2.06
1986	2.11
1987	2.17
1988	2.23
1989	2.28
1990	2.34
1991	2.4
1992	2.47
1993	2.53
1994	2.59
1995	2.66
1996	2.73
1997	2.8
1998	2.87
1999	2.94
2000	3.01
2001	3.08
2002	3.16
2003	3.24
2004	3.32
2005	3.4
2006	3.48
2007	3.56
2008	3.64
2009	3.73
2010	3.81
2011	3.9
2012	3.99
2013	4.08
2014	4.17
2015	4.27