Year	Years
1970	2.01
1971	2.07
1972	2.14
1973	2.2
1974	2.27
1975	2.34
1976	2.41
1977	2.48
1978	2.55
1979	2.63
1980	2.7
1981	2.78
1982	2.86
1983	2.94
1984	3.03
1985	3.11
1986	3.2
1987	3.29
1988	3.38
1989	3.48
1990	3.57
1991	3.67
1992	3.77
1993	3.87
1994	3.98
1995	4.08
1996	4.19
1997	4.3
1998	4.41
1999	4.52
2000	4.64
2001	4.75
2002	4.87
2003	5
2004	5.12
2005	5.25
2006	5.38
2007	5.51
2008	5.65
2009	5.78
2010	5.92
2011	6.06
2012	6.21
2013	6.35
2014	6.5
2015	6.65