Year	Years
1970	1.44
1971	1.49
1972	1.53
1973	1.57
1974	1.62
1975	1.67
1976	1.71
1977	1.76
1978	1.81
1979	1.86
1980	1.91
1981	1.96
1982	2.01
1983	2.06
1984	2.11
1985	2.17
1986	2.22
1987	2.27
1988	2.32
1989	2.37
1990	2.43
1991	2.48
1992	2.53
1993	2.57
1994	2.62
1995	2.67
1996	2.71
1997	2.76
1998	2.81
1999	2.86
2000	2.92
2001	2.98
2002	3.04
2003	3.1
2004	3.17
2005	3.24
2006	3.31
2007	3.39
2008	3.46
2009	3.54
2010	3.62
2011	3.71
2012	3.8
2013	3.89
2014	3.98
2015	4.07