Year	Years
1970	1.47
1971	1.51
1972	1.55
1973	1.59
1974	1.63
1975	1.67
1976	1.72
1977	1.76
1978	1.8
1979	1.84
1980	1.89
1981	1.93
1982	1.97
1983	2.01
1984	2.05
1985	2.09
1986	2.13
1987	2.17
1988	2.2
1989	2.23
1990	2.26
1991	2.29
1992	2.31
1993	2.33
1994	2.35
1995	2.36
1996	2.38
1997	2.4
1998	2.43
1999	2.46
2000	2.49
2001	2.53
2002	2.57
2003	2.62
2004	2.67
2005	2.72
2006	2.78
2007	2.83
2008	2.9
2009	2.96
2010	3.03
2011	3.09
2012	3.17
2013	3.24
2014	3.32
2015	3.39