Year	Years
1970	1.42
1971	1.45
1972	1.49
1973	1.53
1974	1.57
1975	1.61
1976	1.66
1977	1.7
1978	1.74
1979	1.79
1980	1.83
1981	1.88
1982	1.93
1983	1.98
1984	2.03
1985	2.08
1986	2.14
1987	2.19
1988	2.25
1989	2.3
1990	2.36
1991	2.42
1992	2.48
1993	2.54
1994	2.6
1995	2.67
1996	2.74
1997	2.8
1998	2.87
1999	2.94
2000	3.01
2001	3.08
2002	3.16
2003	3.23
2004	3.31
2005	3.39
2006	3.47
2007	3.55
2008	3.63
2009	3.72
2010	3.8
2011	3.89
2012	3.98
2013	4.07
2014	4.16
2015	4.25