Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 25346 | Metric tons | NA |
| 2004 | 30319 | Metric tons | 19.62% |
| 2005 | 29029 | Metric tons | -4.25% |
| 2006 | 27110 | Metric tons | -6.61% |
| 2007 | 32600 | Metric tons | 20.25% |
| 2008 | 30595 | Metric tons | -6.15% |
| 2009 | 31612 | Metric tons | 3.32% |
| 2010 | 34126 | Metric tons | 7.95% |
| 2011 | 29000 | Metric tons | -15.02% |
| 2012 | 30000 | Metric tons | 3.45% |
| 2013 | 30000 | Metric tons | 0.00% |
