Year	Years
1970	1.6
1971	1.65
1972	1.7
1973	1.75
1974	1.81
1975	1.86
1976	1.92
1977	1.98
1978	2.05
1979	2.11
1980	2.18
1981	2.25
1982	2.33
1983	2.4
1984	2.48
1985	2.57
1986	2.65
1987	2.74
1988	2.83
1989	2.93
1990	3.03
1991	3.13
1992	3.24
1993	3.35
1994	3.47
1995	3.59
1996	3.7
1997	3.81
1998	3.92
1999	4.03
2000	4.14
2001	4.25
2002	4.37
2003	4.48
2004	4.59
2005	4.7
2006	4.82
2007	4.93
2008	5.04
2009	5.15
2010	5.27
2011	5.38
2012	5.49
2013	5.6
2014	5.72
2015	5.83