Year	Years
1970	1.41
1971	1.45
1972	1.5
1973	1.55
1974	1.6
1975	1.65
1976	1.7
1977	1.76
1978	1.81
1979	1.87
1980	1.93
1981	1.99
1982	2.06
1983	2.12
1984	2.19
1985	2.26
1986	2.33
1987	2.4
1988	2.47
1989	2.55
1990	2.63
1991	2.71
1992	2.79
1993	2.87
1994	2.96
1995	3.04
1996	3.13
1997	3.23
1998	3.32
1999	3.41
2000	3.51
2001	3.61
2002	3.71
2003	3.82
2004	3.92
2005	4.03
2006	4.14
2007	4.25
2008	4.37
2009	4.49
2010	4.61
2011	4.73
2012	4.85
2013	4.98
2014	5.1
2015	5.23