|
Month
|
2011
|
2010
|
2009
|
| January | 1.68 | 1.65 | 1.52 |
| February | 1.68 | 1.65 | 1.52 |
| March | 1.68 | 1.65 | 1.52 |
| April | 1.68 | 1.64 | 1.52 |
| May | 1.68 | 1.64 | 1.52 |
| June | 1.68 | 1.64 | 1.52 |
| July | 1.64 | 1.39 | |
| August | 1.51 | 1.64 | 1.58 |
| September | 1.64 | 1.58 | |
| October | 1.64 | 1.58 | |
| November | 1.63 | 1.65 | |
| December | 1.63 | 1.65 |