Year	Years
1970	1.6
1971	1.65
1972	1.7
1973	1.76
1974	1.81
1975	1.87
1976	1.93
1977	1.99
1978	2.05
1979	2.12
1980	2.18
1981	2.25
1982	2.32
1983	2.39
1984	2.47
1985	2.54
1986	2.62
1987	2.7
1988	2.78
1989	2.87
1990	2.95
1991	3.04
1992	3.13
1993	3.23
1994	3.32
1995	3.42
1996	3.52
1997	3.62
1998	3.73
1999	3.84
2000	3.95
2001	4.06
2002	4.17
2003	4.29
2004	4.4
2005	4.52
2006	4.64
2007	4.77
2008	4.89
2009	5.02
2010	5.15
2011	5.28
2012	5.41
2013	5.55
2014	5.68
2015	5.82