Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 100 | Thousand metric tons | NA |
| 2003 | 166 | Thousand metric tons | 66.00% |
| 2004 | 193.600006103516 | Thousand metric tons | 16.63% |
| 2005 | 253.100006103516 | Thousand metric tons | 30.73% |
| 2006 | 281.5 | Thousand metric tons | 11.22% |
| 2007 | 313.100006103516 | Thousand metric tons | 11.23% |
| 2008 | 190 | Thousand metric tons | -39.32% |
| 2009 | 195 | Thousand metric tons | 2.63% |
| 2010 | 288 | Thousand metric tons | 47.69% |
| 2011 | 299 | Thousand metric tons | 3.82% |
| 2012 | 232 | Thousand metric tons | -22.41% |
