Year	Years
1970	5.01
1971	5.11
1972	5.22
1973	5.32
1974	5.43
1975	5.53
1976	5.64
1977	5.75
1978	5.86
1979	5.96
1980	6.07
1981	6.18
1982	6.29
1983	6.4
1984	6.51
1985	6.62
1986	6.73
1987	6.84
1988	6.95
1989	7.05
1990	7.16
1991	7.27
1992	7.38
1993	7.48
1994	7.59
1995	7.7
1996	7.81
1997	7.92
1998	8.03
1999	8.15
2000	8.27
2001	8.39
2002	8.51
2003	8.64
2004	8.77
2005	8.89
2006	9.02
2007	9.16
2008	9.29
2009	9.43
2010	9.56
2011	9.7
2012	9.84
2013	9.98
2014	10.12
2015	10.26