Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 10228 | Thousand metric tons | NA |
| 2004 | 10180 | Thousand metric tons | -0.47 % |
| 2005 | 10236 | Thousand metric tons | 0.55 % |
| 2006 | 10736 | Thousand metric tons | 4.88 % |
| 2007 | 10960 | Thousand metric tons | 2.09 % |
| 2008 | 10137 | Thousand metric tons | -7.51 % |
| 2009 | 7674 | Thousand metric tons | -24.30 % |
