Changes in the Company's common stock from January 1 through December 31 are presented below (in millions):
| 2013 | 2012 | 2011 | |||||||||||||||||||
| Balance at beginning of year | 297.7 | 315.0 | 348.3 | ||||||||||||||||||
| Shares issued under the Company’s equity-based compensation plan | 4.2 | 4.8 | 4.0 | ||||||||||||||||||
| Shares repurchased and retired | (24.0) | (22.1) | (37.3) | ||||||||||||||||||
| Balance at end of year | 277.9 | 297.7 | 315.0 | ||||||||||||||||||