Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 72600 | Metric tons, gross weight | NA |
| 2003 | 98000 | Metric tons, gross weight | 34.99% |
| 2004 | 160300 | Metric tons, gross weight | 63.57% |
| 2005 | 170000 | Metric tons, gross weight | 6.05% |
| 2006 | 210120 | Metric tons, gross weight | 23.60% |
| 2007 | 323570 | Metric tons, gross weight | 53.99% |
| 2008 | 225373 | Metric tons, gross weight | -30.35% |
| 2009 | 283558 | Metric tons, gross weight | 25.82% |
| 2010 | 328322 | Metric tons, gross weight | 15.79% |
| 2011 | 330938 | Metric tons, gross weight | 0.80% |
| 2012 | 330000 | Metric tons, gross weight | -0.28% |
