Year	Years
1970	1.31
1971	1.36
1972	1.41
1973	1.46
1974	1.51
1975	1.56
1976	1.62
1977	1.67
1978	1.73
1979	1.79
1980	1.86
1981	1.92
1982	1.99
1983	2.06
1984	2.14
1985	2.21
1986	2.29
1987	2.38
1988	2.46
1989	2.55
1990	2.64
1991	2.74
1992	2.83
1993	2.93
1994	3.04
1995	3.15
1996	3.26
1997	3.38
1998	3.49
1999	3.61
2000	3.73
2001	3.86
2002	3.98
2003	4.1
2004	4.23
2005	4.36
2006	4.49
2007	4.62
2008	4.74
2009	4.88
2010	5.01
2011	5.14
2012	5.27
2013	5.4
2014	5.53
2015	5.66