| Año | Valor |
|---|---|
| 1980-01-01 | 31.392967 |
| 1981-01-01 | 30.880914 |
| 1982-01-01 | 30.400255 |
| 1983-01-01 | 29.949189 |
| 1984-01-01 | 29.521258 |
| 1985-01-01 | 29.117389 |
| 1986-01-01 | 28.735141 |
| 1987-01-01 | 28.367908 |
| 1988-01-01 | 28.014070 |
| 1989-01-01 | 27.676128 |
| 1990-01-01 | 27.357479 |
| 1991-01-01 | 27.058434 |
| 1992-01-01 | 26.799712 |
| 1993-01-01 | 26.724968 |
| 1994-01-01 | 26.667395 |
| 1995-01-01 | 26.625040 |
| 1996-01-01 | 26.597504 |
| 1997-01-01 | 26.582922 |
| 1998-01-01 | 26.583334 |
| 1999-01-01 | 26.591857 |
Fuente: World Bank