1895   7.74
  1896   8.61
  1897   8.06
  1898   7.95
  1899   8.52
  1900   9.68
  1901   9.36
  1902   8.67
  1903   7.93
  1904   8.83
  1905   8.56
  1906   8.73
  1907   9.21
  1908   7.95
  1909   8.35
  1910   9.81
  1911   8.09
  1912   7.75
  1913   7.90
  1914   8.88
  1915   8.47
  1916   7.67
  1917   7.50
  1918   8.42
  1919   8.34
  1920   7.89
  1921   9.50
  1922   8.10
  1923   7.85
  1924   8.00
  1925   8.77
  1926   9.36
  1927   8.86
  1928   8.94
  1929   8.23
  1930   8.02
  1931   8.57
  1932   7.60
  1933   8.36
  1934  10.72
  1935   8.84
  1936   9.13
  1937   8.34
  1938   8.90
  1939   8.94
  1940   9.77
  1941   8.50
  1942   8.38
  1943   9.58
  1944   8.09
  1945   8.56
  1946   9.21
  1947   9.00
  1948   8.31
  1949   7.97
  1950   9.10
  1951   8.58
  1952   8.56
  1953   9.36
  1954   9.90
  1955   8.08
  1956   9.13
  1957   8.71
  1958   9.76
  1959   9.29
  1960   9.08
  1961   8.86
  1962   8.90
  1963   9.19
  1964   7.94
  1965   8.52
  1966   9.11
  1967   8.84
  1968   8.38
  1969   9.18
  1970   8.81
  1971   8.44
  1972   9.20
  1973   8.24
  1974   9.03
  1975   7.88
  1976   8.85
  1977   9.72
  1978   9.16
  1979   8.52
  1980   9.48
  1981  10.36
  1982   8.40
  1983   9.17
  1984   8.10
  1985   8.71
  1986  10.16
  1987   9.36
  1988   9.31
  1989   9.38
  1990   9.51
  1991   8.81
  1992   9.60
  1993   8.24
  1994  10.11
  1995   9.86
  1996  10.10
  1997   9.45
  1998   9.60
  1999   9.98
  2000  10.56
  2001  10.31
  2002   9.64
  2003  10.63
  2004   9.54
  2005   9.93
  2006   9.85
  2007  10.21
  2008   9.25
  2009   8.93 
  2010   9.11
%http://www.wrcc.dri.edu/cgi-bin/divplot1_form.pl?4203