| Entidades calificadoras | Fecha | Largo plazo Moneda Extranjera | Largo plazo Moneda Local |
| Moody´s | 14 Oct 2011 | Ba2 | Ba1 |
| Fitch Ratings | 1 Jul 2011 | BB- | BB |
| Moody´s | 1 Jul 2011 | Ba2 | Ba1 |
| Fitch Ratings | 12 May 2011 | BB- | BB |
| Fitch Ratings | 24 Nov 2010 | BB- | BB |
| Moody's | 30 Jul 2010 | WR | Ba1 |
| Fitch Ratings | 1 Jul 2010 | BB- | BB |
| Moody's | 1 Jul 2010 | Ba2 | Ba1 |
| Moody's | 23 Nov 2009 | WR | Ba1 |
| Moody's | 5 Jun 2009 | WR | Ba1 |
| Standard & Poor's | 4 May 2009 | NR | NR |
| Moody's | 24 Feb 2009 | WR | Baa2 |
| Standard & Poor's | 12 Feb 2009 | B+ | B+ |
| Fitch Ratings | 15 Ene 2009 | BB- | BB |
| Fitch Ratings | 11 Ene 2009 | BB- | BB |
| Moody's | 23 Dic 2008 | Ba2 | Baa2 |
| Fitch Ratings | 18 Dic 2008 | BB- | BB |
| Fitch Ratings | 24 Nov 2008 | BB+ | BBB- |
| Standard & Poor's | 5 Nov 2008 | BB | BB |
| Standard & Poor's | 27 Dic 2007 | BB | BB+ |
| Fitch Ratings | 2 Ago 2006 | BB+ | BBB- |
| Moody's | 7 Jun 2006 | Ba2 | WR |
| Fitch Ratings | 24 Abr 2006 | BB | BBB- |
| Moody's | 16 Jun 2005 | Ba3 | WR |
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