Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 471 | Thousand metric tons | NA |
| 2003 | 572 | Thousand metric tons | 21.44% |
| 2004 | 518.9990234375 | Thousand metric tons | -9.27% |
| 2005 | 543.072021484375 | Thousand metric tons | 4.64% |
| 2006 | 570.031005859375 | Thousand metric tons | 4.96% |
| 2007 | 608.192016601563 | Thousand metric tons | 6.69% |
| 2008 | 676 | Thousand metric tons | 11.15% |
| 2009 | 670 | Thousand metric tons | -0.89% |
| 2010 | 534 | Thousand metric tons | -20.30% |
| 2011 | 538 | Thousand metric tons | 0.75% |
| 2012 | 600 | Thousand metric tons | 11.52% |
