Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 380000 | Metric tons | NA |
| 2004 | 370000 | Metric tons | -2.63% |
| 2005 | 380000 | Metric tons | 2.70% |
| 2006 | 370000 | Metric tons | -2.63% |
| 2007 | 360000 | Metric tons | -2.70% |
| 2008 | 350000 | Metric tons | -2.78% |
| 2009 | 340000 | Metric tons | -2.86% |
