Year	Years
1970	0.5
1971	0.52
1972	0.54
1973	0.57
1974	0.59
1975	0.62
1976	0.64
1977	0.67
1978	0.7
1979	0.73
1980	0.76
1981	0.79
1982	0.83
1983	0.87
1984	0.9
1985	0.95
1986	0.99
1987	1.03
1988	1.08
1989	1.13
1990	1.19
1991	1.24
1992	1.3
1993	1.36
1994	1.42
1995	1.48
1996	1.54
1997	1.59
1998	1.64
1999	1.7
2000	1.76
2001	1.82
2002	1.87
2003	1.94
2004	2
2005	2.06
2006	2.13
2007	2.2
2008	2.27
2009	2.34
2010	2.41
2011	2.48
2012	2.56
2013	2.64
2014	2.72
2015	2.8