Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 283991 | Metric tons, gross weight | NA |
| 2003 | 376862 | Metric tons, gross weight | 32.70% |
| 2004 | 593476 | Metric tons, gross weight | 57.48% |
| 2005 | 616534 | Metric tons, gross weight | 3.89% |
| 2006 | 562739 | Metric tons, gross weight | -8.73% |
| 2007 | 627772 | Metric tons, gross weight | 11.56% |
| 2008 | 664347 | Metric tons, gross weight | 5.83% |
| 2009 | 365210 | Metric tons, gross weight | -45.03% |
| 2010 | 520129 | Metric tons, gross weight | 42.42% |
| 2011 | 542512 | Metric tons, gross weight | 4.30% |
| 2012 | 543000 | Metric tons, gross weight | 0.09% |
