Year	Years
1970	1.5
1971	1.55
1972	1.6
1973	1.65
1974	1.7
1975	1.75
1976	1.81
1977	1.87
1978	1.93
1979	1.99
1980	2.05
1981	2.11
1982	2.18
1983	2.25
1984	2.32
1985	2.39
1986	2.47
1987	2.54
1988	2.62
1989	2.7
1990	2.78
1991	2.87
1992	2.95
1993	3.04
1994	3.13
1995	3.23
1996	3.33
1997	3.42
1998	3.53
1999	3.63
2000	3.73
2001	3.84
2002	3.95
2003	4.06
2004	4.18
2005	4.29
2006	4.41
2007	4.53
2008	4.65
2009	4.77
2010	4.9
2011	5.03
2012	5.16
2013	5.29
2014	5.42
2015	5.56