Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 603498 | Metric tons | NA |
| 2003 | 557082 | Metric tons | -7.69% |
| 2004 | 562795 | Metric tons | 1.03% |
| 2005 | 595383 | Metric tons | 5.79% |
| 2006 | 603295 | Metric tons | 1.33% |
| 2007 | 596249 | Metric tons | -1.17% |
| 2008 | 605399 | Metric tons | 1.53% |
| 2009 | 493700 | Metric tons | -18.45% |
| 2010 | 521900 | Metric tons | 5.71% |
| 2011 | 565200 | Metric tons | 8.30% |
| 2012 | 577700 | Metric tons | 2.21% |
