Year	Years
1800	459.5
1954	57.1
1955	53.7
1956	50.6
1957	47.7
1958	45
1959	42.7
1960	40.7
1961	39.1
1962	37.8
1963	36.5
1964	35.4
1965	34.3
1966	33.1
1967	31.8
1968	30.5
1969	29.1
1970	27.8
1971	26.4
1972	25.1
1973	23.8
1974	22.6
1975	21.4
1976	20.2
1977	19.2
1978	18.3
1979	17.6
1980	16.9
1981	16.3
1982	15.7
1983	15.1
1984	14.5
1985	13.9
1986	13.3
1987	12.7
1988	12.2
1989	11.8
1990	11.4
1991	11
1992	10.6
1993	10.2
1994	9.9
1995	9.5
1996	9.1
1997	8.7
1998	8.4
1999	8.1
2000	7.8
2001	7.5
2002	7.3
2003	7.1
2004	7
2005	6.9
2006	6.8
2007	6.7
2008	6.6
2009	6.5
2010	6.4
2011	6.3
2012	6.2
2013	6.1