| Año | Valor |
|---|---|
| 1987-01-01 | 10.000000 |
| 1988-01-01 | 9.584609 |
| 1989-01-01 | 9.205553 |
| 1990-01-01 | 8.858265 |
| 1991-01-01 | 8.538911 |
| 1992-01-01 | 8.244252 |
| 1993-01-01 | 7.971530 |
| 1994-01-01 | 7.718383 |
| 1995-01-01 | 7.482777 |
| 1996-01-01 | 7.262949 |
| 1997-01-01 | 7.057366 |
| 1998-01-01 | 6.864686 |
| 1999-01-01 | 6.683733 |
| 2000-01-01 | 6.660269 |
| 2001-01-01 | 6.637161 |
| 2002-01-01 | 6.614402 |
| 2003-01-01 | 6.591984 |
| 2004-01-01 | 6.569899 |
| 2005-01-01 | 6.548140 |
| 2006-01-01 | 6.526699 |
Fuente: World Bank