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 |
| 3.51 | 3.44 | 3.32 | 3.58 | 3.61 | 3.31 | 3.45 | 3.15 | 2.76 | 2.72 | 2.62 | 3.23 |
Relativeerror (%) | 2.6 | 3.0 | 3.1 | 2.3 | 2.5 | 2.8 | 2.4 | 2.9 | 3.0 | 2.2 | 1.5 | 1.6 |