Year	Years
1970	1.99
1971	2.06
1972	2.12
1973	2.18
1974	2.25
1975	2.32
1976	2.39
1977	2.46
1978	2.54
1979	2.61
1980	2.69
1981	2.77
1982	2.85
1983	2.94
1984	3.03
1985	3.12
1986	3.21
1987	3.3
1988	3.4
1989	3.5
1990	3.6
1991	3.7
1992	3.81
1993	3.92
1994	4.04
1995	4.15
1996	4.27
1997	4.4
1998	4.53
1999	4.66
2000	4.79
2001	4.92
2002	5.06
2003	5.19
2004	5.33
2005	5.47
2006	5.62
2007	5.76
2008	5.91
2009	6.06
2010	6.21
2011	6.36
2012	6.51
2013	6.67
2014	6.82
2015	6.98