Year	Years
1970	1.12
1971	1.16
1972	1.2
1973	1.24
1974	1.28
1975	1.32
1976	1.36
1977	1.41
1978	1.45
1979	1.5
1980	1.55
1981	1.6
1982	1.65
1983	1.71
1984	1.76
1985	1.82
1986	1.88
1987	1.94
1988	2
1989	2.07
1990	2.13
1991	2.2
1992	2.27
1993	2.34
1994	2.42
1995	2.5
1996	2.58
1997	2.66
1998	2.75
1999	2.84
2000	2.92
2001	3.02
2002	3.11
2003	3.2
2004	3.3
2005	3.4
2006	3.5
2007	3.6
2008	3.71
2009	3.81
2010	3.92
2011	4.03
2012	4.14
2013	4.26
2014	4.37
2015	4.49