Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 21724 | Metric tons | NA |
| 2004 | 22337 | Metric tons | 2.82% |
| 2005 | 20226 | Metric tons | -9.45% |
| 2006 | 21165 | Metric tons | 4.64% |
| 2007 | 16911 | Metric tons | -20.10% |
| 2008 | 16600 | Metric tons | -1.84% |
| 2009 | 13756 | Metric tons | -17.13% |
| 2010 | 14000 | Metric tons | 1.77% |
| 2011 | 17667 | Metric tons | 26.19% |
| 2012 | 18127 | Metric tons | 2.60% |
| 2013 | 21051 | Metric tons | 16.13% |
