Year	Years
1970	1.96
1971	2.02
1972	2.08
1973	2.14
1974	2.21
1975	2.28
1976	2.35
1977	2.42
1978	2.5
1979	2.57
1980	2.65
1981	2.73
1982	2.82
1983	2.9
1984	2.99
1985	3.08
1986	3.18
1987	3.27
1988	3.37
1989	3.48
1990	3.58
1991	3.69
1992	3.8
1993	3.91
1994	4.03
1995	4.15
1996	4.28
1997	4.42
1998	4.55
1999	4.69
2000	4.83
2001	4.98
2002	5.13
2003	5.27
2004	5.43
2005	5.58
2006	5.73
2007	5.89
2008	6.05
2009	6.21
2010	6.37
2011	6.53
2012	6.7
2013	6.86
2014	7.02
2015	7.19