Year	Years
1970	1.62
1971	1.68
1972	1.74
1973	1.81
1974	1.88
1975	1.95
1976	2.03
1977	2.1
1978	2.18
1979	2.27
1980	2.36
1981	2.45
1982	2.55
1983	2.65
1984	2.76
1985	2.87
1986	2.99
1987	3.11
1988	3.24
1989	3.38
1990	3.52
1991	3.67
1992	3.83
1993	3.99
1994	4.17
1995	4.35
1996	4.52
1997	4.68
1998	4.85
1999	5.02
2000	5.19
2001	5.36
2002	5.53
2003	5.7
2004	5.87
2005	6.04
2006	6.22
2007	6.39
2008	6.56
2009	6.73
2010	6.9
2011	7.07
2012	7.24
2013	7.41
2014	7.58
2015	7.75