Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 313637 | Metric tons, gross weight | NA |
| 2003 | 229294 | Metric tons, gross weight | -26.89% |
| 2004 | 506421 | Metric tons, gross weight | 120.86% |
| 2005 | 688377 | Metric tons, gross weight | 35.93% |
| 2006 | 1059901 | Metric tons, gross weight | 53.97% |
| 2007 | 1678932 | Metric tons, gross weight | 58.40% |
| 2008 | 1885712 | Metric tons, gross weight | 12.32% |
| 2009 | 1573993 | Metric tons, gross weight | -16.53% |
| 2010 | 1904461 | Metric tons, gross weight | 21.00% |
| 2011 | 2901027 | Metric tons, gross weight | 52.33% |
| 2012 | 2500000 | Metric tons, gross weight | -13.82% |
