Year	Years
1970	0.97
1971	1.01
1972	1.04
1973	1.07
1974	1.11
1975	1.15
1976	1.19
1977	1.23
1978	1.27
1979	1.31
1980	1.35
1981	1.4
1982	1.44
1983	1.49
1984	1.54
1985	1.59
1986	1.64
1987	1.7
1988	1.75
1989	1.81
1990	1.87
1991	1.93
1992	1.99
1993	2.06
1994	2.13
1995	2.2
1996	2.27
1997	2.35
1998	2.42
1999	2.5
2000	2.59
2001	2.67
2002	2.75
2003	2.84
2004	2.93
2005	3.02
2006	3.11
2007	3.2
2008	3.3
2009	3.4
2010	3.5
2011	3.6
2012	3.7
2013	3.81
2014	3.92
2015	4.03