Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 893 | Metric tons | NA |
| 2003 | 827 | Metric tons | -7.39% |
| 2004 | 733 | Metric tons | -11.37% |
| 2005 | 832 | Metric tons | 13.51% |
| 2006 | 806.0830078125 | Metric tons | -3.12% |
| 2007 | 722.927001953125 | Metric tons | -10.32% |
| 2008 | 645.627014160156 | Metric tons | -10.69% |
| 2009 | 618.140991210938 | Metric tons | -4.26% |
| 2010 | 552.059997558594 | Metric tons | -10.69% |
| 2011 | 650.648986816406 | Metric tons | 17.86% |
| 2012 | 963.137023925781 | Metric tons | 48.03% |
