Year Measure 1900 3581 1901 3548 1902 3607 1903 3539 1904 3530 1905 3604 1906 3692 1907 3730 1908 3547 1909 3596 1910 3676 1911 3754 1912 3796 1913 3923 1914 3927 1915 4216 1916 4292 1917 4322 1918 4352 1919 3883 1920 3626 1921 3539 1922 3696 1923 3794 1924 3923 1925 4101 1926 3935 1927 4237 1928 4270 1929 4387 1930 4337 1931 4096 1932 4104 1933 4207 1934 4470 1935 4623 1936 4811 1937 4957 1938 4996 1939 4992 1940 5465 1941 5964 1942 6090 1943 6173 1944 5903 1945 5625 1946 5377 1947 5265 1948 5378 1949 5545 1950 5532 1951 5679 1952 5653 1953 5856 1954 6074 1955 6272 1956 6321 1957 6391 1958 6350 1959 6569 1960 6892 1961 7060 1962 7067 1963 7294 1964 7627 1965 7774 1966 7880 1967 8011 1968 8299 1969 8412 1970 8584 1971 8722 1972 9003 1973 9586 1974 9454 1975 9444 1976 9658 1977 9872 1978 10230 1979 10500 1980 10310 1981 10160 1982 10330 1983 10690 1984 10940 1985 11220 1986 13460 1987 14580 1988 16060 1989 16910 1990 17360 1991 17380 1992 17350 1993 17630 1994 18160 1995 18750 1996 20010 1997 21530 1998 24220 1999 27280 2000 28480 2001 29740 2002 31190 2003 32870 2004 34260 2005 35950 2006 37360 2007 39640