| Año | Valor |
|---|---|
| 1987-01-01 | 8.640544 |
| 1988-01-01 | 8.485251 |
| 1989-01-01 | 8.421673 |
| 1990-01-01 | 8.442825 |
| 1991-01-01 | 8.530029 |
| 1992-01-01 | 8.335246 |
| 1993-01-01 | 8.367583 |
| 1994-01-01 | 8.443806 |
| 1995-01-01 | 8.532610 |
| 1996-01-01 | 8.606572 |
| 1997-01-01 | 8.740292 |
| 1998-01-01 | 8.891779 |
| 1999-01-01 | 8.658021 |
| 2000-01-01 | 8.807192 |
| 2001-01-01 | 8.887437 |
| 2002-01-01 | 9.039651 |
| 2003-01-01 | 9.215250 |
| 2004-01-01 | 9.528509 |
| 2005-01-01 | 9.876431 |
| 2006-01-01 | 10.274434 |
Fuente: World Bank