Year	Years
1970	1.31
1971	1.36
1972	1.41
1973	1.46
1974	1.51
1975	1.56
1976	1.62
1977	1.68
1978	1.74
1979	1.8
1980	1.86
1981	1.93
1982	2
1983	2.07
1984	2.15
1985	2.23
1986	2.31
1987	2.39
1988	2.48
1989	2.57
1990	2.66
1991	2.76
1992	2.86
1993	2.96
1994	3.07
1995	3.18
1996	3.28
1997	3.39
1998	3.49
1999	3.6
2000	3.71
2001	3.82
2002	3.93
2003	4.04
2004	4.15
2005	4.26
2006	4.38
2007	4.5
2008	4.61
2009	4.73
2010	4.85
2011	4.97
2012	5.1
2013	5.22
2014	5.35
2015	5.48