| Date | Value |
|---|---|
| Dec 31, 2015 07:43 | 415 ppm |
| Dec 2, 2015 11:32 | 415 ppm |
| Sep 16, 2015 11:44 | 410 ppm |
| May 7, 2015 10:37 | 450 ppm |
| Apr 6, 2015 06:26 | 440 ppm |
| Mar 25, 2015 11:35 | 460 ppm |
| Mar 13, 2015 06:58 | 440 ppm |
| Mar 8, 2015 10:00 | 480 ppm |
| Mar 1, 2015 07:25 | 440 ppm |
| Feb 27, 2015 10:41 | 440 ppm |