Year	Years
1970	0.98
1971	1.02
1972	1.07
1973	1.12
1974	1.17
1975	1.22
1976	1.27
1977	1.33
1978	1.4
1979	1.46
1980	1.53
1981	1.61
1982	1.69
1983	1.77
1984	1.86
1985	1.96
1986	2.07
1987	2.18
1988	2.3
1989	2.43
1990	2.56
1991	2.71
1992	2.87
1993	3.05
1994	3.23
1995	3.43
1996	3.59
1997	3.75
1998	3.91
1999	4.07
2000	4.23
2001	4.39
2002	4.54
2003	4.7
2004	4.86
2005	5.01
2006	5.17
2007	5.32
2008	5.48
2009	5.63
2010	5.79
2011	5.94
2012	6.09
2013	6.24
2014	6.4
2015	6.55