human
schlumberger limited and subsidiaries shares of common stock issued in treasury shares outstanding (stated in millions).
|  | Issued | In Treasury | Shares Outstanding |
| --------- | --------- | --------- | --------- |
| Balance, January 1, 2008 | 1,334 | (138) | 1,196 |
| Shares sold to optionees less shares exchanged | – | 5 | 5 |
| Shares issued under employee stock purchase plan | – | 2 | 2 |
| Stock repurchase program | – | (21) | (21) |
| Issued on conversions of debentures | – | 12 | 12 |
| Balance, December 31, 2008 | 1,334 | (140) | 1,194 |
| Shares sold to optionees less shares exchanged | – | 4 | 4 |
| Vesting of restricted stock | – | 1 | 1 |
| Shares issued under employee stock purchase plan | – | 4 | 4 |
| Stock repurchase program | – | (8) | (8) |
| Balance, December 31, 2009 | 1,334 | (139) | 1,195 |
| Acquisition of Smith International, Inc. | 100 | 76 | 176 |
| Shares sold to optionees less shares exchanged | – | 6 | 6 |
| Shares issued under employee stock purchase plan | – | 3 | 3 |
| Stock repurchase program | – | (27) | (27) |
| Issued on conversions of debentures | – | 8 | 8 |
| Balance, December 31, 2010 | 1,434 | (73) | 1,361 |
see the notes to consolidated financial statements part ii, item 8.
Please compute the result.
what is the sum of balances of outstanding shares for 2009 and 2010?
assistant
2556.0
human
what is the average?
assistant
1278.0
human
what about the sum of balances of outstanding shares for december 2008 and december 2009?
assistant
2389.0
human
what about the average for these years?
assistant
1194.5