1926 13.5130 1927 13.4300 1928 13.2810 1929 13.0730 1930 12.1300 1931 10.8920 1932 9.45000 1933 8.96200 1934 9.79400 1935 9.98600 1936 10.8140 1937 10.8420 1938 10.5730 1939 10.6480