Year	Years
1970	1.63
1971	1.7
1972	1.77
1973	1.85
1974	1.94
1975	2.03
1976	2.12
1977	2.22
1978	2.32
1979	2.43
1980	2.54
1981	2.66
1982	2.79
1983	2.92
1984	3.06
1985	3.21
1986	3.36
1987	3.52
1988	3.68
1989	3.86
1990	4.04
1991	4.22
1992	4.42
1993	4.61
1994	4.81
1995	5.02
1996	5.21
1997	5.4
1998	5.6
1999	5.79
2000	5.99
2001	6.18
2002	6.37
2003	6.57
2004	6.76
2005	6.96
2006	7.15
2007	7.34
2008	7.53
2009	7.71
2010	7.9
2011	8.08
2012	8.26
2013	8.43
2014	8.61
2015	8.78