Year	Years
1970	1.4
1971	1.44
1972	1.49
1973	1.53
1974	1.58
1975	1.63
1976	1.69
1977	1.74
1978	1.8
1979	1.86
1980	1.92
1981	1.99
1982	2.06
1983	2.13
1984	2.21
1985	2.29
1986	2.38
1987	2.47
1988	2.56
1989	2.67
1990	2.78
1991	2.89
1992	3.02
1993	3.16
1994	3.3
1995	3.46
1996	3.6
1997	3.74
1998	3.87
1999	4.01
2000	4.14
2001	4.27
2002	4.41
2003	4.54
2004	4.67
2005	4.8
2006	4.93
2007	5.07
2008	5.2
2009	5.33
2010	5.47
2011	5.6
2012	5.73
2013	5.87
2014	6
2015	6.14