| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
1 | | | | | | | 14.8 | 18.5 | 19.7 | 11.2 | 8.0 | 0.1 |
2 | | | | | | | 15.7 | 18.7 | 18.8 | 15.9 | 14.9 | -0.3 |
3 | | | | | | | 18.2 | 19.7 | 18.3 | 13.2 | 13.5 | 8.4 |
4 | | | | | | | 18.4 | 19.6 | 16.7 | 13.0 | 12.2 | 8.6 |
5 | | | | | | | 18.3 | 20.4 | 17.1 | 11.8 | 6.7 | 6.4 |
6 | | | | | | | 19.7 | 20.3 | 16.0 | 10.8 | 4.4 | 3.8 |
7 | | | | | | | 20.1 | 24.1 | 19.3 | 11.7 | 6.7 | 5.2 |
8 | | | | | | | 18.3 | 20.2 | 21.6 | 10.6 | 10.3 | 5.4 |
9 | | | | | | | 15.8 | 20.8 | 19.2 | 12.9 | 15.7 | 9.8 |
10 | | | | | | | 16.4 | 20.6 | 19.4 | 15.9 | 12.9 | 7.3 |
11 | | | | | | | 15.9 | | 16.7 | 13.3 | 9.1 | 2.3 |
12 | | | | | | | 19.3 | | 14.9 | 12.2 | 6.9 | -1.3 |
13 | | | | | | | 19.2 | 19.6 | 14.3 | 12.2 | 7.1 | 4.1 |
14 | | | | | | | 19.0 | 15.5 | 18.0 | 11.6 | 7.1 | 5.4 |
15 | | | | | | | 16.9 | 21.0 | 21.6 | 13.7 | 7.9 | 7.6 |
16 | | | | | | | 18.7 | 20.0 | 20.9 | 14.2 | 8.3 | 10.3 |
17 | | | | | | | 17.9 | 18.2 | 12.9 | 12.1 | 8.9 | 5.4 |
18 | | | | | | | 21.4 | 18.7 | 8.2 | 12.1 | 10.7 | 3.6 |
19 | | | | | | | 21.7 | 19.6 | 12.1 | 11.4 | 9.7 | 6.2 |
20 | | | | | | | 20.2 | 16.8 | 10.7 | 11.1 | 5.7 | 9.4 |
21 | | | | | | | 19.7 | 17.5 | 12.5 | 12.2 | 4.6 | 9.9 |
22 | | | | | | | 19.1 | 19.7 | 7.6 | 20.3 | 7.7 | 9.4 |
23 | | | | | | | 19.7 | 15.4 | 8.2 | 18.4 | 1.6 | 8.8 |
24 | | | | | | | 29.6 | 15.4 | 10.9 | 20.7 | 1.8 | 12.1 |
25 | | | | | | | 29.6 | 17.7 | 15.2 | 17.9 | 6.1 | 12.0 |
26 | | | | | | | 24.8 | | 13.7 | 15.7 | 5.6 | 12.8 |
27 | | | | | | 18.1 | 23.2 | | 12.9 | 12.8 | 3.3 | 10.5 |
28 | | | | | | 17.5 | 19.3 | | 12.2 | 13.0 | 3.1 | 7.3 |
29 | | | | | | 18.2 | 19.9 | | 17.5 | 12.2 | 7.4 | 12.3 |
30 | | | | | | 17.4 | 20.1 | 18.2 | 12.3 | 9.3 | 3.5 | 12.7 |
31 | | | | | | | 18.0 | 19.8 | | 9.1 | | 12.3 |