Year	Years
1970	1.97
1971	2.02
1972	2.07
1973	2.13
1974	2.18
1975	2.24
1976	2.3
1977	2.36
1978	2.42
1979	2.48
1980	2.55
1981	2.62
1982	2.69
1983	2.76
1984	2.83
1985	2.91
1986	2.98
1987	3.06
1988	3.14
1989	3.23
1990	3.32
1991	3.41
1992	3.5
1993	3.6
1994	3.69
1995	3.8
1996	3.91
1997	4.02
1998	4.13
1999	4.24
2000	4.36
2001	4.48
2002	4.59
2003	4.71
2004	4.83
2005	4.95
2006	5.08
2007	5.2
2008	5.32
2009	5.44
2010	5.57
2011	5.69
2012	5.82
2013	5.94
2014	6.07
2015	6.19