Year	Years
1970	1.71
1971	1.76
1972	1.82
1973	1.89
1974	1.95
1975	2.02
1976	2.09
1977	2.16
1978	2.24
1979	2.32
1980	2.4
1981	2.49
1982	2.58
1983	2.67
1984	2.77
1985	2.87
1986	2.98
1987	3.1
1988	3.22
1989	3.34
1990	3.47
1991	3.61
1992	3.76
1993	3.91
1994	4.07
1995	4.24
1996	4.42
1997	4.59
1998	4.76
1999	4.92
2000	5.09
2001	5.25
2002	5.41
2003	5.57
2004	5.72
2005	5.87
2006	6.03
2007	6.18
2008	6.33
2009	6.47
2010	6.62
2011	6.77
2012	6.91
2013	7.05
2014	7.2
2015	7.34