1910    21.380
1911    23.140
1912    26.000
1913    16.180
1914    19.060
1915    27.320
1916    19.760
1917    29.140
1918    16.820
1919    19.580
1920    24.920
1921    20.780
1922    10.580
1923    16.900
1924    31.960
1925    22.300
1926    18.400
1927    22.040
1928    25.400
1929    14.120
1930    15.940
1931    23.540
1932    11.000
1933    17.580
1934    37.960
1935    12.720
1936    33.620
1937    15.100
1938    11.700
1939    15.120
1940    20.760
1941    35.280
1942    14.840
1943    11.120
1944    12.680
1945    21.940
1946     9.100
1947     9.020
1948    16.480
1949    12.280
1950    28.640
1951    24.000
1952    12.240
1953    18.480
1954    28.940
1955    22.660
1956    22.440
1957    14.580
1958    15.420
1959    13.640
1960    10.960
1961    20.960
1962     6.100
1963    20.420
1964    16.180
1965    24.100
1966    14.200
1967    21.040
1968    13.960
1969     8.560
1970     7.800
1971     9.620
1972     9.260
1973    20.400
1974    14.600
1975    21.900
1976    20.420
1977    19.680
1978    13.860
1979    16.920
1980    17.460
1981    13.160
1982    13.180
1983    21.340
1984    16.740
1985    10.160
1986    15.760
1987    20.320
1988    24.620
1989    18.920
1990    15.920
1991    23.760
1992    31.240
1993    26.100
1994    17.580
1995    18.560
1996    19.040
1997    24.700
1998    33.740
1999    17.840
2000    21.580
2001    23.200
2002    25.720
2003    23.320
2004    18.260
2005    20.900
2006    27.960
2007    32.100
2008    17.560
2009    20.260
2010    35.620
2011    38.440
2012    39.600