Year	Years
1970	1.92
1971	1.98
1972	2.03
1973	2.09
1974	2.15
1975	2.22
1976	2.28
1977	2.34
1978	2.41
1979	2.47
1980	2.54
1981	2.61
1982	2.68
1983	2.75
1984	2.82
1985	2.89
1986	2.97
1987	3.04
1988	3.11
1989	3.19
1990	3.26
1991	3.33
1992	3.41
1993	3.48
1994	3.56
1995	3.63
1996	3.71
1997	3.78
1998	3.87
1999	3.95
2000	4.04
2001	4.13
2002	4.22
2003	4.32
2004	4.42
2005	4.52
2006	4.62
2007	4.73
2008	4.84
2009	4.95
2010	5.07
2011	5.19
2012	5.31
2013	5.43
2014	5.56
2015	5.68