Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 566090 | Metric tons, gross weight | NA |
| 2003 | 549040 | Metric tons, gross weight | -3.01% |
| 2004 | 579780 | Metric tons, gross weight | 5.60% |
| 2005 | 571103 | Metric tons, gross weight | -1.50% |
| 2006 | 548713 | Metric tons, gross weight | -3.92% |
| 2007 | 556100 | Metric tons, gross weight | 1.35% |
| 2008 | 613543 | Metric tons, gross weight | 10.33% |
| 2009 | 246817 | Metric tons, gross weight | -59.77% |
| 2010 | 598000 | Metric tons, gross weight | 142.28% |
| 2011 | 692527 | Metric tons, gross weight | 15.81% |
| 2012 | 425217 | Metric tons, gross weight | -38.60% |
