Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 606 | Thousand metric tons | NA |
| 2003 | 597 | Thousand metric tons | -1.49% |
| 2004 | 753.099975585938 | Thousand metric tons | 26.15% |
| 2005 | 832.099975585938 | Thousand metric tons | 10.49% |
| 2006 | 1065.40002441406 | Thousand metric tons | 28.04% |
| 2007 | 1105.40002441406 | Thousand metric tons | 3.75% |
| 2008 | 1076 | Thousand metric tons | -2.66% |
| 2009 | 583 | Thousand metric tons | -45.82% |
| 2010 | 843 | Thousand metric tons | 44.60% |
| 2011 | 996 | Thousand metric tons | 18.15% |
| 2012 | 1000 | Thousand metric tons | 0.40% |
