| Month | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 |
| Level | Level | Level | Level | Level | Level | |
| Jan. | −423.190 | −424.240 | −425.604 | −426.760 | −427.910 | −428.90 |
| Feb. | −423.020 | −424.330 | −425.710 | −426.755 | −427.960 | −428.88 |
| Mar. | −423.100 | −424.360 | −425.825 | −426.815 | −427.970 | −428.89 |
| Apr. | −423.180 | −424.435 | NA | −426.910 | −428.070 | −428.96 |
| May | −423.270 | −424.540 | −425.990 | −426.990 | −428.040 | −429.02 |
| June | −423.360 | −424.670 | −426.126 | −427.103 | −428.110 | −429.12 |
| July | −423.500 | −424.790 | −426.282 | −427.330 | −428.400 | −429.32 |
| Aug. | −423.700 | −424.920 | −426.415 | −427.467 | −428.485 | −429.45 |
| Sep. | −423.780 | −425.045 | −426.560 | −427.568 | −428.590 | −429.51 |
| Oct. | −423.880 | −425.170 | −426.632 | −427.680 | −428.750 | −429.60 |
| Nov. | −424.030 | −425.300 | −426.750 | −427.760 | −428.800 | −429.66 |
| Dec. | −424.130 | −425.520 | −426.880 | −427.830 | −428.810 | −429.84 |
| Level difference | −0.94 | −1.28 | −1.28 | −1.07 | −0.90 | −0.94 |