Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 14400 | Metric tons | NA |
| 2003 | 14900 | Metric tons | 3.47% |
| 2004 | 15500 | Metric tons | 4.03% |
| 2005 | 15000 | Metric tons | -3.23% |
| 2006 | 13000 | Metric tons | -13.33% |
| 2007 | 13600 | Metric tons | 4.62% |
| 2008 | 13440 | Metric tons | -1.18% |
| 2009 | 14600 | Metric tons | 8.63% |
| 2010 | 14700 | Metric tons | 0.68% |
| 2011 | 16000 | Metric tons | 8.84% |
| 2012 | 16000 | Metric tons | 0.00% |
