Year Years 1800 498.9 1801 498.9 1802 498.9 1803 498.9 1804 498.9 1805 498.9 1806 498.9 1807 498.9 1808 498.9 1809 498.9 1810 498.9 1811 498.9 1812 498.9 1813 498.9 1814 498.9 1815 498.9 1816 498.9 1817 498.9 1818 498.9 1819 498.9 1820 498.9 1821 498.9 1822 498.9 1823 498.9 1824 498.9 1825 498.9 1826 498.9 1827 498.9 1828 498.9 1829 498.9 1830 498.9 1831 498.9 1832 498.9 1833 498.9 1834 498.9 1835 498.9 1836 498.9 1837 498.9 1838 498.9 1839 498.9 1840 498.9 1841 498.9 1842 498.9 1843 498.9 1844 498.9 1845 498.9 1846 498.9 1847 498.9 1848 498.9 1849 498.9 1850 498.9 1851 498.9 1852 498.9 1853 498.9 1854 498.9 1855 498.9 1856 498.9 1857 498.9 1858 498.9 1859 498.9 1860 498.9 1861 498.9 1862 498.9 1863 498.9 1864 498.9 1865 498.9 1866 498.9 1867 498.9 1868 498.9 1869 498.9 1870 498.9 1871 498.9 1872 498.9 1873 498.9 1874 498.9 1875 498.9 1876 498.9 1877 498.9 1878 498.9 1879 498.9 1880 498.9 1881 498.9 1882 498.9 1883 498.9 1884 498.9 1885 498.9 1886 498.9 1887 498.9 1888 498.9 1889 498.9 1890 498.9 1891 498.9 1892 498.9 1893 498.9 1894 498.9 1895 498.8 1896 498.8 1897 498.6 1898 498.4 1899 498.1 1900 497.8 1901 497.4 1902 496.9 1903 496.3 1904 495.6 1905 494.9 1906 494.1 1907 493.2 1908 492.2 1909 491.1 1910 490.1 1911 488.9 1912 487.8 1913 486.6 1914 485.4 1915 484.2 1916 483.1 1917 481.9 1918 480.7 1919 479.6 1920 478.4 1921 477.2 1922 476.1 1923 474.9 1924 473.7 1925 472.5 1926 457.6 1927 443 1928 428.8 1929 414.9 1930 401.5 1931 388.3 1932 375.5 1933 363 1934 350.8 1935 338.9 1936 327.2 1937 315.8 1938 304.7 1939 293.8 1940 283.1 1950 120 1951 114.9 1952 109.5 1953 104.1 1954 98.7 1955 93.6 1956 88.6 1957 84 1958 79.7 1959 75.9 1960 72.5 1961 69.4 1962 66.7 1963 64.4 1964 62.3 1965 60.5 1966 59 1967 57.7 1968 56.7 1969 55.9 1970 55.3 1971 54.9 1972 54.4 1973 54 1974 53.4 1975 52.5 1976 51.3 1977 49.8 1978 48 1979 46 1980 44 1981 42 1982 40.2 1983 38.4 1984 36.9 1985 35.6 1986 34.3 1987 33.1 1988 32 1989 31 1990 30 1991 29 1992 28.1 1993 27.4 1994 26.8 1995 26.4 1996 25.9 1997 25.5 1998 25.1 1999 24.8 2000 24.4 2001 24 2002 23.6 2003 23.3 2004 23.1 2005 23 2006 23.1 2007 23.2 2008 23.4 2009 23.6 2010 23.7 2011 23.8 2012 23.8 2013 23.6