| Año | Valor |
|---|---|
| 1990-01-01 | 29.621400 |
| 1991-01-01 | 31.407100 |
| 1992-01-01 | 32.729800 |
| 1993-01-01 | 34.900700 |
| 1994-01-01 | 36.945900 |
| 1995-01-01 | 29.214200 |
| 1996-01-01 | 29.057600 |
| 1997-01-01 | 33.436500 |
| 1998-01-01 | 30.771900 |
| 1999-01-01 | 30.054700 |
| 2000-01-01 | 29.388100 |
| 2001-01-01 | 27.879500 |
| 2002-01-01 | 29.071600 |
| 2003-01-01 | 30.019900 |
| 2004-01-01 | 31.384500 |
| 2005-01-01 | 31.948100 |
| 2006-01-01 | 32.992500 |
| 2007-01-01 | 35.019900 |
| 2008-01-01 | 36.171300 |
| 2009-01-01 | 37.571300 |
Fuente: World Bank