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 | 34 | Thousand metric tons | -66.00% |
| 2004 | 38.939998626709 | Thousand metric tons | 14.53% |
| 2005 | 43.265998840332 | Thousand metric tons | 11.11% |
| 2006 | 45.2220001220703 | Thousand metric tons | 4.52% |
| 2007 | 49.2290000915527 | Thousand metric tons | 8.86% |
| 2008 | 44.4280014038086 | Thousand metric tons | -9.75% |
| 2009 | 36.9280014038086 | Thousand metric tons | -16.88% |
| 2010 | 65.245002746582 | Thousand metric tons | 76.68% |
| 2011 | 72.1529998779297 | Thousand metric tons | 10.59% |
| 2012 | 75 | Thousand metric tons | 3.95% |
| 2013 | 100 | Thousand metric tons | 33.33% |
