| Año | Valor |
|---|---|
| 1987-01-01 | 5.000000 |
| 1988-01-01 | 4.666375 |
| 1989-01-01 | 4.361933 |
| 1990-01-01 | 4.083006 |
| 1991-01-01 | 3.826515 |
| 1992-01-01 | 3.589857 |
| 1993-01-01 | 3.370819 |
| 1994-01-01 | 3.167502 |
| 1995-01-01 | 2.978272 |
| 1996-01-01 | 2.801716 |
| 1997-01-01 | 2.636600 |
| 1998-01-01 | 2.481848 |
| 1999-01-01 | 2.336514 |
| 2000-01-01 | 2.249342 |
| 2001-01-01 | 2.163495 |
| 2002-01-01 | 2.078942 |
| 2003-01-01 | 1.995656 |
| 2004-01-01 | 1.913606 |
| 2005-01-01 | 1.832767 |
| 2006-01-01 | 1.753112 |
Fuente: World Bank