Year Measure 1800 378.4 1820 378.4 1885 481.3 1886 461.7 1887 538.6 1888 517 1889 479.6 1890 476.6 1891 435.6 1892 475.7 1893 537.9 1894 610.2 1895 563.4 1896 619.2 1897 607.4 1898 622.2 1899 658.8 1900 643.2 1901 657.7 1902 713.1 1903 662.4 1904 730.9 1905 645.5 1906 615.6 1907 590.2 1908 643.1 1909 666.2 1910 709.2 1911 653.8 1912 704.8 1913 738.8 1914 703.9 1915 722.8 1916 700 1917 583.3 1918 486 1919 405 1920 384.5 1921 365 1922 395.9 1923 429.3 1924 465.6 1925 505 1926 547.6 1927 593.9 1928 644.1 1929 698.6 1930 728.5 1931 733.4 1932 720.5 1933 745.9 1934 812.5 1935 926.9 1936 987.8 1937 1067 1938 1062 1939 1102 1940 1054 1946 928.4 1947 1029 1948 1160 1949 1264 1950 1366 1951 1346 1952 1406 1953 1439 1954 1480 1955 1575 1956 1692 1957 1693 1958 1784 1959 1729 1960 1855 1961 1927 1962 1947 1963 1874 1964 2087 1965 2179 1966 2259 1967 2334 1968 2446 1969 2457 1970 2621 1971 2665 1972 2653 1973 2849 1974 2880 1975 2836 1976 2917 1977 2934 1978 2957 1979 2893 1980 2849 1981 2828 1982 2849 1983 2890 1984 2875 1985 2851 1986 2917 1987 2905 1988 2918 1989 2922 1990 2809 1991 2437 1992 1443 1993 1376 1994 1499 1995 1632 1996 1732 1997 1791 1998 1928 1999 1993 2000 2114 2001 2328 2002 2692 2003 3079 2004 3414 2005 3903 2006 4413 2007 5012 2008 5347 2009 4545 2010 4599 2011 4767 2012 5059 2013 5224 2014 5385 2015 5561 2016 5742 2017 5930 2018 6124