Year	Years
1960	138.6
1961	127.3
1962	117.1
1963	108.1
1964	100.1
1965	93.1
1966	86.8
1967	81.1
1968	75.7
1969	70.1
1970	64.3
1971	58
1972	51.5
1973	45.2
1974	39.3
1975	34.2
1976	29.8
1977	26.3
1978	23.5
1979	21.3
1980	19.7
1981	18.5
1982	17.6
1983	17.1
1984	16.9
1985	16.8
1986	16.8
1987	16.9
1988	17
1989	17.1
1990	17.2
1991	17.3
1992	17.3
1993	17.3
1994	17.3
1995	17.1
1996	16.9
1997	16.7
1998	16.4
1999	16.1
2000	15.8
2001	15.5
2002	15.1
2003	14.8
2004	14.5
2005	14.1
2006	13.8
2007	13.5
2008	13.1
2009	12.8
2010	12.4
2011	12.1
2012	11.7
2013	11.4