Year	Years
1970	1.74
1971	1.8
1972	1.85
1973	1.91
1974	1.97
1975	2.03
1976	2.09
1977	2.16
1978	2.22
1979	2.29
1980	2.36
1981	2.43
1982	2.5
1983	2.57
1984	2.65
1985	2.73
1986	2.81
1987	2.89
1988	2.97
1989	3.06
1990	3.15
1991	3.24
1992	3.33
1993	3.42
1994	3.52
1995	3.61
1996	3.71
1997	3.82
1998	3.92
1999	4.03
2000	4.14
2001	4.25
2002	4.36
2003	4.48
2004	4.59
2005	4.71
2006	4.84
2007	4.96
2008	5.09
2009	5.22
2010	5.35
2011	5.48
2012	5.62
2013	5.75
2014	5.89
2015	6.04