1897,27.14
1898,29.99
1899,24.04
1900,22.29
1901,23.43
1902,21.34
1903,20.81
1904,21.62
1905,27.57
1906,31.60
1907,29.65
1908,28.00
1909,23.93
1910,20.16
1911,23.53
1912,28.53
1913,25.55
1914,28.21
1915,35.45
1916,31.61
1917,23.93
1918,20.88
1919,29.62
1920,33.48
1921,30.07
1922,25.23
1923,21.82
1924,26.70
1925,25.83
1926,26.86
1927,28.93
1928,24.86
1929,26.87
1930,28.45
1931,29.91
1932,34.19
1933,29.13
1934,22.21
1935,23.31
1936,26.65
1937,26.05
1938,26.53
1939,25.38
1940,25.25
1941,39.51
1942,41.95
1943,27.50
1944,24.84
1945,23.73
1946,22.49
1947,22.64
1948,22.92
1949,28.00
1950,26.96
1951,19.25
1952,19.92
1953,20.40
1954,19.66
1955,22.71
1956,18.77
1957,19.47
1958,30.64
1959,30.10
1960,25.36
1961,28.09
1962,27.30
1963,25.17
1964,22.48
1965,23.55
1966,27.05
1967,25.19
1968,24.02
1969,26.68
1970,26.91
1971,23.53
1972,26.20
1973,31.31
1974,27.04
1975,26.79
1976,26.72
1977,23.40
1978,25.23
1979,30.23
1980,29.92
1981,26.47
1982,27.52
1983,26.60
1984,28.89
1985,34.50
1986,36.89
1987,36.51
1988,35.75
1989,28.31
1990,24.92
1991,30.81
1992,34.42
1993,32.36
1994,27.25
1995,27.46
1996,27.40
1997,29.48
1998,29.87
1999,31.14
2000,27.33
2001,24.02
2002,25.43
2003,20.48
2004,25.83
2005,32.81
2006,31.60
2007,30.14
2008,28.62
2009,25.02
2010,27.90
2011,23.60
2012,18.67