Year	Years
1970	0.46
1971	0.48
1972	0.51
1973	0.53
1974	0.55
1975	0.58
1976	0.61
1977	0.64
1978	0.67
1979	0.7
1980	0.74
1981	0.78
1982	0.82
1983	0.87
1984	0.92
1985	0.97
1986	1.03
1987	1.1
1988	1.17
1989	1.24
1990	1.32
1991	1.41
1992	1.5
1993	1.6
1994	1.69
1995	1.79
1996	1.86
1997	1.92
1998	1.98
1999	2.05
2000	2.11
2001	2.17
2002	2.24
2003	2.31
2004	2.37
2005	2.44
2006	2.51
2007	2.58
2008	2.65
2009	2.72
2010	2.79
2011	2.87
2012	2.94
2013	3.02
2014	3.1
2015	3.18