Year	Years
1970	1.48
1971	1.52
1972	1.56
1973	1.6
1974	1.63
1975	1.68
1976	1.72
1977	1.76
1978	1.8
1979	1.84
1980	1.89
1981	1.93
1982	1.98
1983	2.03
1984	2.07
1985	2.12
1986	2.17
1987	2.22
1988	2.27
1989	2.32
1990	2.38
1991	2.43
1992	2.48
1993	2.54
1994	2.6
1995	2.65
1996	2.72
1997	2.78
1998	2.85
1999	2.92
2000	2.99
2001	3.06
2002	3.13
2003	3.2
2004	3.28
2005	3.35
2006	3.43
2007	3.51
2008	3.59
2009	3.67
2010	3.76
2011	3.84
2012	3.93
2013	4.02
2014	4.11
2015	4.2