Month | Jan. | Feb. | Mar. | Apr. | May | Jun. | Jul. | Aug. | Sep. | Oct. | Nov. | Dec. |
| 3.42 | 3.34 | 3.22 | 3.50 | 3.52 | 3.21 | 3.37 | 3.06 | 2.68 | 2.66 | 2.58 | 3.18 |
| 3.43 | 3.34 | 3.23 | 3.53 | 3.54 | 3.22 | 3.46 | 3.11 | 2.72 | 2.65 | 2.56 | 3.05 |
Relativeerror (%) | 1.1 | 0.1 | 0.3 | 0.8 | 0.5 | 0.3 | 2.6 | 1.6 | 1.5 | 0.4 | 0.8 | 4.0 |