|
Month
|
2011
|
2010
|
2009
|
| January | 1.79 | 1.74 | |
| February | 1.79 | 1.74 | |
| March | 1.78 | 1.74 | |
| April | 1.78 | 1.74 | |
| May | 1.78 | 1.70 | |
| June | 1.90 | 1.70 | |
| July | 1.70 | ||
| August | 1.90 | 1.70 | |
| September | 1.70 | ||
| October | 1.70 | 1.74 | |
| November | 1.70 | 1.74 | |
| December | 1.70 | 1.74 |