Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 15000 | Thousand metric tons | NA |
| 2004 | 15254 | Thousand metric tons | 1.69% |
| 2005 | 16817 | Thousand metric tons | 10.25% |
| 2006 | 18784 | Thousand metric tons | 11.70% |
| 2007 | 18519 | Thousand metric tons | -1.41% |
| 2008 | 18400 | Thousand metric tons | -0.64% |
| 2009 | 15600 | Thousand metric tons | -15.22% |
