Year	Years
1970	2.03
1971	2.1
1972	2.17
1973	2.24
1974	2.31
1975	2.39
1976	2.46
1977	2.54
1978	2.62
1979	2.7
1980	2.79
1981	2.87
1982	2.96
1983	3.05
1984	3.14
1985	3.24
1986	3.33
1987	3.43
1988	3.53
1989	3.63
1990	3.73
1991	3.84
1992	3.94
1993	4.05
1994	4.16
1995	4.26
1996	4.38
1997	4.49
1998	4.6
1999	4.72
2000	4.84
2001	4.96
2002	5.08
2003	5.2
2004	5.33
2005	5.46
2006	5.59
2007	5.72
2008	5.85
2009	5.98
2010	6.12
2011	6.26
2012	6.39
2013	6.53
2014	6.67
2015	6.82