Year	Years
1970	1.4
1971	1.43
1972	1.47
1973	1.51
1974	1.55
1975	1.6
1976	1.64
1977	1.68
1978	1.73
1979	1.78
1980	1.82
1981	1.87
1982	1.92
1983	1.98
1984	2.03
1985	2.08
1986	2.14
1987	2.2
1988	2.26
1989	2.32
1990	2.38
1991	2.44
1992	2.51
1993	2.58
1994	2.65
1995	2.72
1996	2.79
1997	2.87
1998	2.95
1999	3.03
2000	3.11
2001	3.19
2002	3.27
2003	3.35
2004	3.44
2005	3.53
2006	3.61
2007	3.7
2008	3.79
2009	3.88
2010	3.98
2011	4.07
2012	4.16
2013	4.26
2014	4.36
2015	4.46