Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 749339 | Metric tons, gross weight | NA |
| 2003 | 637099 | Metric tons, gross weight | -14.98% |
| 2004 | 621269 | Metric tons, gross weight | -2.48% |
| 2005 | 819903 | Metric tons, gross weight | 31.97% |
| 2006 | 712908 | Metric tons, gross weight | -13.05% |
| 2007 | 663593 | Metric tons, gross weight | -6.92% |
| 2008 | 442584 | Metric tons, gross weight | -33.30% |
| 2009 | 193673 | Metric tons, gross weight | -56.24% |
| 2010 | 510000 | Metric tons, gross weight | 163.33% |
| 2011 | 599079 | Metric tons, gross weight | 17.47% |
| 2012 | 550000 | Metric tons, gross weight | -8.19% |
