| 日期 | 代碼 | 券商 | 原評等→降級後評等 | 新目標價 |
| 2014/2/9 | DO | Global Hunter Securities | Neutral >> Sell | $61 >> $38 |
| 2014/2/4 | DO | Wunderlich | Buy >> Hold | 50 |
| 2014/1/9 | DO | Howard Weil | Sector Outperform >> Sector Perform | 75 |
| 2012/10/10 | DO | FBR Capital | Outperform >> Mkt Perform | |
| 2011/12/19 | DO | Barclays Capital | Equal Weight >> Underweight | $60 >> $61 |