Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 197.5 | Thousand metric tons | NA |
| 2003 | 164 | Thousand metric tons | -16.96% |
| 2004 | 244.300003051758 | Thousand metric tons | 48.96% |
| 2005 | 206 | Thousand metric tons | -15.68% |
| 2006 | 214 | Thousand metric tons | 3.88% |
| 2007 | 180.399993896484 | Thousand metric tons | -15.70% |
| 2008 | 211 | Thousand metric tons | 16.96% |
| 2009 | 151 | Thousand metric tons | -28.44% |
| 2010 | 180.5 | Thousand metric tons | 19.54% |
| 2011 | 171 | Thousand metric tons | -5.26% |
| 2012 | 175 | Thousand metric tons | 2.34% |
