Year	Years
1970	1.28
1971	1.31
1972	1.35
1973	1.38
1974	1.42
1975	1.46
1976	1.5
1977	1.54
1978	1.58
1979	1.63
1980	1.67
1981	1.71
1982	1.76
1983	1.81
1984	1.86
1985	1.91
1986	1.96
1987	2.02
1988	2.07
1989	2.13
1990	2.18
1991	2.24
1992	2.31
1993	2.37
1994	2.43
1995	2.5
1996	2.57
1997	2.65
1998	2.72
1999	2.8
2000	2.87
2001	2.95
2002	3.03
2003	3.11
2004	3.19
2005	3.28
2006	3.36
2007	3.45
2008	3.53
2009	3.62
2010	3.71
2011	3.8
2012	3.89
2013	3.99
2014	4.08
2015	4.18