| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
| 1901 | 75.0 | 80.0 | 85.0 | 87.0 | 90.0 | 100.0 | 101.0 | 102.0 | 94.0 | 91.0 | 80.0 | 76.0 | 102.0 |
| 1902 | 71.0 | 73.0 | 84.0 | 87.0 | 90.0 | 98.0 | 93.0 | 98.0 | 95.0 | 89.0 | 81.0 | 77.0 | 98.0 |
| 1903 | 81.0 | 74.0 | 80.0 | 86.0 | 87.0 | 94.0 | 95.0 | 96.0 | 95.0 | 87.0 | 85.0 | 74.0 | 96.0 |
| 1904 | 73.0 | 84.0 | 90.0 | 85.0 | 91.0 | 95.0 | 94.0 | 98.0 | 96.0 | 95.0 | 82.0 | 81.0 | 98.0 |
| 1905 | 74.0 | 75.0 | 84.0 | 86.0 | 89.0 | 95.0 | 93.0 | 95.0 | 95.0 | 92.0 | 83.0 | 62.0 | 95.0 |
| 1906 | 78.0 | 75.0 | 80.0 | 85.0 | 92.0 | 95.0 | 94.0 | 92.0 | 94.0 | 82.0 | 83.0 | 80.0 | 95.0 |
| 1907 | 80.0 | 87.0 | 85.0 | 92.0 | 92.0 | 97.0 | 101.0 | 99.0 | 94.0 | 79.0 | 79.0 | 101.0 | |
| 1908 | 75.0 | 76.0 | 89.0 | 86.0 | 88.0 | 94.0 | 96.0 | 96.0 | 96.0 | 85.0 | 84.0 | 79.0 | 96.0 |
| 1909 | 82.0 | 81.0 | 87.0 | 86.0 | 88.0 | 94.0 | 98.0 | 109.0 | 103.0 | 96.0 | 85.0 | 80.0 | 109.0 |
| 1910 | 77.0 | 72.0 | 89.0 | 85.0 | 88.0 | 93.0 | 97.0 | 99.0 | 97.0 | 93.0 | 85.0 | 99.0 | |
| 1911 | 84.0 | 82.0 | 92.0 | 87.0 | 96.0 | 100.0 | 96.0 | 97.0 | 102.0 | 96.0 | 87.0 | 70.0 | 102.0 |
| 1912 | 76.0 | 78.0 | 81.0 | 89.0 | 91.0 | 92.0 | 102.0 | 96.0 | 97.0 | 92.0 | 81.0 | 70.0 | 102.0 |
| 1913 | 74.0 | 81.0 | 85.0 | 87.0 | 89.0 | 95.0 | 101.0 | 101.0 | 97.0 | 88.0 | 80.0 | 73.0 | 101.0 |
| 1914 | 79.0 | 74.0 | 79.0 | 88.0 | 89.0 | 101.0 | 101.0 | 96.0 | 94.0 | 90.0 | 83.0 | 68.0 | 101.0 |
| 1915 | 71.0 | 73.0 | 82.0 | 86.0 | 97.0 | 99.0 | 96.0 | 98.0 | 91.0 | 90.0 | 85.0 | 76.0 | 99.0 |
| 1916 | 78.0 | 79.0 | 90.0 | 84.0 | 90.0 | 94.0 | 98.0 | 99.0 | 97.0 | 91.0 | 84.0 | 80.0 | 99.0 |
| 1917 | 80.0 | 85.0 | 85.0 | 85.0 | 93.0 | 101.0 | 105.0 | 105.0 | 100.0 | 95.0 | 82.0 | 85.0 | 105.0 |
| 1918 | 79.0 | 90.0 | 90.0 | 88.0 | 92.0 | 110.0 | 107.0 | 105.0 | 99.0 | 91.0 | 80.0 | 77.0 | 110.0 |
| 1919 | 70.0 | 77.0 | 84.0 | 90.0 | 90.0 | 96.0 | 99.0 | 100.0 | 98.0 | 92.0 | 85.0 | 82.0 | 100.0 |
| 1920 | 79.0 | 79.0 | 83.0 | 93.0 | 96.0 | 98.0 | 102.0 | 95.0 | 100.0 | 92.0 | 84.0 | 70.0 | 102.0 |
| 1921 | 72.0 | 79.0 | 81.0 | 78.0 | 98.0 | 97.0 | 99.0 | 104.0 | 98.0 | 96.0 | 91.0 | 82.0 | 104.0 |
| 1922 | 78.0 | 85.0 | 85.0 | 89.0 | 93.0 | 99.0 | 102.0 | 103.0 | 102.0 | 96.0 | 88.0 | 95.0 | 103.0 |
| 1923 | 79.0 | 83.0 | 81.0 | 88.0 | 95.0 | 96.0 | 104.0 | 105.0 | 98.0 | 96.0 | 79.0 | 82.0 | 105.0 |
| 1924 | 75.0 | 82.0 | 85.0 | 90.0 | 92.0 | 98.0 | 106.0 | 107.0 | 103.0 | 91.0 | 83.0 | 83.0 | 107.0 |
| 1925 | 68.0 | 76.0 | 82.0 | 89.0 | 91.0 | 98.0 | 100.0 | 104.0 | 100.0 | 92.0 | 80.0 | 73.0 | 104.0 |
| 1926 | 68.0 | 77.0 | 80.0 | 83.0 | 91.0 | 92.0 | 95.0 | 97.0 | 95.0 | 91.0 | 79.0 | 77.0 | 97.0 |
| 1927 | 77.0 | 79.0 | 81.0 | 85.0 | 92.0 | 91.0 | 96.0 | 101.0 | 100.0 | 89.0 | 84.0 | 80.0 | 101.0 |
| 1928 | 77.0 | 73.0 | 87.0 | 80.0 | 93.0 | 91.0 | 97.0 | 97.0 | 94.0 | 93.0 | 78.0 | 76.0 | 97.0 |
| 1929 | 75.0 | 69.0 | 88.0 | 96.0 | 87.0 | 94.0 | 96.0 | 98.0 | 95.0 | 89.0 | 79.0 | 75.0 | 98.0 |
| 1930 | 70.0 | 81.0 | 76.0 | 90.0 | 88.0 | 99.0 | 101.0 | 101.0 | 94.0 | 84.0 | 79.0 | 67.0 | 101.0 |