Year	Years
1970	1.2
1971	1.24
1972	1.28
1973	1.32
1974	1.36
1975	1.4
1976	1.45
1977	1.49
1978	1.54
1979	1.59
1980	1.63
1981	1.69
1982	1.74
1983	1.79
1984	1.85
1985	1.9
1986	1.96
1987	2.02
1988	2.08
1989	2.14
1990	2.2
1991	2.27
1992	2.34
1993	2.41
1994	2.48
1995	2.55
1996	2.62
1997	2.7
1998	2.78
1999	2.85
2000	2.94
2001	3.02
2002	3.11
2003	3.2
2004	3.29
2005	3.38
2006	3.47
2007	3.57
2008	3.67
2009	3.77
2010	3.88
2011	3.98
2012	4.09
2013	4.2
2014	4.31
2015	4.43