Year	Years
1970	0.44
1971	0.46
1972	0.48
1973	0.51
1974	0.54
1975	0.57
1976	0.6
1977	0.63
1978	0.67
1979	0.71
1980	0.75
1981	0.8
1982	0.85
1983	0.91
1984	0.97
1985	1.03
1986	1.11
1987	1.18
1988	1.27
1989	1.36
1990	1.46
1991	1.57
1992	1.68
1993	1.8
1994	1.92
1995	2.04
1996	2.13
1997	2.22
1998	2.31
1999	2.4
2000	2.49
2001	2.59
2002	2.68
2003	2.78
2004	2.87
2005	2.97
2006	3.07
2007	3.17
2008	3.28
2009	3.38
2010	3.49
2011	3.59
2012	3.7
2013	3.81
2014	3.93
2015	4.04