Year	Years
1970	1.93
1971	1.98
1972	2.03
1973	2.08
1974	2.13
1975	2.19
1976	2.24
1977	2.3
1978	2.36
1979	2.42
1980	2.48
1981	2.54
1982	2.61
1983	2.67
1984	2.74
1985	2.81
1986	2.88
1987	2.95
1988	3.03
1989	3.1
1990	3.18
1991	3.26
1992	3.34
1993	3.42
1994	3.5
1995	3.59
1996	3.67
1997	3.76
1998	3.85
1999	3.94
2000	4.03
2001	4.12
2002	4.21
2003	4.31
2004	4.41
2005	4.5
2006	4.6
2007	4.71
2008	4.81
2009	4.92
2010	5.02
2011	5.13
2012	5.24
2013	5.35
2014	5.46
2015	5.58