| Month | Average | 25% | 50% | 60% | 75% | 85% |
| January | 0.74 | 1.02 | 0.62 | 0.52 | 0.33 | 0.03 |
| February | 0.58 | 0.94 | 0.49 | 0.34 | 0.08 | −0.18 |
| March | 0.13 | 0.55 | −0.05 | −0.27 | −0.49 | −0.72 |
| April | −0.50 | −0.16 | −0.77 | −0.95 | −1.15 | −1.36 |
| May | −0.85 | −0.42 | −1.04 | −1.26 | −1.55 | −1.74 |
| June | −0.84 | −0.30 | −1.06 | −1.26 | −1.68 | −1.95 |
| July | −0.93 | −0.61 | −1.13 | −1.32 | −1.56 | −1.79 |
| August | −0.45 | 0.00 | −0.59 | −0.86 | −1.05 | −1.24 |
| September | −0.04 | 0.34 | −0.12 | −0.39 | −0.59 | −0.91 |
| October | 0.58 | 1.07 | 0.34 | 0.12 | −0.18 | −0.36 |
| November | 0.69 | 0.85 | 0.52 | 0.38 | 0.28 | 0.16 |
| December | 0.92 | 1.15 | 0.83 | 0.76 | 0.57 | 0.44 |