Year	Years
1970	1.61
1971	1.66
1972	1.72
1973	1.78
1974	1.84
1975	1.9
1976	1.96
1977	2.03
1978	2.1
1979	2.17
1980	2.25
1981	2.32
1982	2.4
1983	2.48
1984	2.57
1985	2.65
1986	2.74
1987	2.83
1988	2.93
1989	3.03
1990	3.13
1991	3.23
1992	3.34
1993	3.45
1994	3.56
1995	3.68
1996	3.8
1997	3.93
1998	4.05
1999	4.18
2000	4.31
2001	4.45
2002	4.58
2003	4.72
2004	4.86
2005	5
2006	5.14
2007	5.28
2008	5.42
2009	5.57
2010	5.71
2011	5.86
2012	6
2013	6.15
2014	6.29
2015	6.44