Year	Years
1970	0.18
1971	0.19
1972	0.2
1973	0.21
1974	0.23
1975	0.24
1976	0.25
1977	0.27
1978	0.28
1979	0.3
1980	0.32
1981	0.34
1982	0.37
1983	0.39
1984	0.42
1985	0.45
1986	0.49
1987	0.52
1988	0.56
1989	0.61
1990	0.66
1991	0.71
1992	0.77
1993	0.83
1994	0.89
1995	0.95
1996	1
1997	1.04
1998	1.09
1999	1.13
2000	1.18
2001	1.23
2002	1.27
2003	1.32
2004	1.37
2005	1.42
2006	1.48
2007	1.53
2008	1.59
2009	1.64
2010	1.7
2011	1.76
2012	1.82
2013	1.88
2014	1.94
2015	2.01