Year	Years
1970	1.97
1971	2.02
1972	2.08
1973	2.13
1974	2.18
1975	2.24
1976	2.3
1977	2.36
1978	2.42
1979	2.48
1980	2.54
1981	2.61
1982	2.67
1983	2.74
1984	2.81
1985	2.88
1986	2.95
1987	3.02
1988	3.1
1989	3.18
1990	3.25
1991	3.34
1992	3.42
1993	3.5
1994	3.59
1995	3.67
1996	3.76
1997	3.86
1998	3.95
1999	4.04
2000	4.14
2001	4.24
2002	4.34
2003	4.44
2004	4.54
2005	4.64
2006	4.75
2007	4.85
2008	4.96
2009	5.07
2010	5.18
2011	5.29
2012	5.4
2013	5.52
2014	5.63
2015	5.75