Year	Years
1970	1.21
1971	1.25
1972	1.28
1973	1.32
1974	1.35
1975	1.39
1976	1.43
1977	1.47
1978	1.51
1979	1.55
1980	1.59
1981	1.63
1982	1.68
1983	1.72
1984	1.77
1985	1.82
1986	1.87
1987	1.92
1988	1.97
1989	2.02
1990	2.08
1991	2.14
1992	2.19
1993	2.25
1994	2.32
1995	2.38
1996	2.45
1997	2.51
1998	2.58
1999	2.65
2000	2.72
2001	2.8
2002	2.87
2003	2.94
2004	3.02
2005	3.1
2006	3.18
2007	3.25
2008	3.34
2009	3.42
2010	3.5
2011	3.59
2012	3.67
2013	3.76
2014	3.85
2015	3.94