Year	Years
1970	1.61
1971	1.65
1972	1.7
1973	1.74
1974	1.79
1975	1.83
1976	1.88
1977	1.93
1978	1.98
1979	2.03
1980	2.09
1981	2.14
1982	2.2
1983	2.26
1984	2.31
1985	2.37
1986	2.43
1987	2.5
1988	2.56
1989	2.63
1990	2.69
1991	2.76
1992	2.83
1993	2.9
1994	2.97
1995	3.05
1996	3.12
1997	3.19
1998	3.27
1999	3.35
2000	3.43
2001	3.51
2002	3.59
2003	3.67
2004	3.76
2005	3.84
2006	3.93
2007	4.02
2008	4.1
2009	4.19
2010	4.29
2011	4.38
2012	4.47
2013	4.57
2014	4.67
2015	4.76