Year	Years
1800	471
1950	128.2
1951	126.6
1952	123.5
1953	120.3
1954	117.1
1955	113.7
1956	110.2
1957	106.7
1958	103.1
1968	29.4
1969	30
1970	30.6
1971	31.2
1972	31.7
1973	32
1974	32.2
1975	32.1
1976	31.9
1977	31.5
1978	31
1979	30.5
1980	29.9
1981	29.4
1982	29
1983	28.6
1984	28.2
1985	27.8
1986	27.3
1987	26.5
1988	25.6
1989	24.5
1990	23.5
1991	22.5
1992	21.5
1993	20.6
1994	19.7
1995	18.7
1996	17.9
1997	17.1
1998	16.5
1999	16.1
2000	15.8
2001	15.6
2002	15.6
2003	15.5
2004	15.4
2005	15.3
2006	15.1
2007	14.9
2008	14.6
2009	14.3
2010	13.9
2011	13.6
2012	13.3
2013	12.9