Year	Years
1970	0.93
1971	0.97
1972	1.01
1973	1.05
1974	1.09
1975	1.13
1976	1.17
1977	1.22
1978	1.27
1979	1.31
1980	1.37
1981	1.42
1982	1.48
1983	1.54
1984	1.6
1985	1.66
1986	1.73
1987	1.8
1988	1.87
1989	1.95
1990	2.03
1991	2.11
1992	2.2
1993	2.29
1994	2.39
1995	2.49
1996	2.6
1997	2.7
1998	2.8
1999	2.91
2000	3.02
2001	3.12
2002	3.23
2003	3.34
2004	3.45
2005	3.57
2006	3.68
2007	3.79
2008	3.91
2009	4.02
2010	4.14
2011	4.26
2012	4.38
2013	4.5
2014	4.62
2015	4.75