Year	Years
1800	459.5
1950	181.3
1951	180
1952	178
1953	174.9
1954	170.2
1955	165.3
1956	159.6
1957	153
1958	145.7
1959	138.6
1960	131.7
1970	75.4
1971	68.7
1972	62.4
1973	56.5
1974	51.2
1975	46.6
1976	42.7
1977	39.5
1978	37.1
1979	35.1
1980	33.5
1981	32.2
1982	31
1983	29.8
1984	28.5
1985	27.3
1986	26.1
1987	25
1988	24
1989	23.2
1990	22.6
1991	22.1
1992	21.6
1993	21.1
1994	20.6
1995	20.1
1996	19.5
1997	19
1998	18.6
1999	18.2
2000	17.9
2001	17.6
2002	17.4
2003	17.3
2004	17.1
2005	17
2006	16.8
2007	16.5
2008	16.2
2009	15.9
2010	15.6
2011	15.2
2012	14.9
2013	14.5