Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 91200 | Metric tons | NA |
| 2004 | 75400 | Metric tons | -17.32% |
| 2005 | 76600 | Metric tons | 1.59% |
| 2006 | 74500 | Metric tons | -2.74% |
| 2007 | 51000 | Metric tons | -31.54% |
| 2008 | 40000 | Metric tons | -21.57% |
| 2009 | 14300 | Metric tons | -64.25% |
| 2010 | 350 | Metric tons | -97.55% |
| 2011 | 120 | Metric tons | -65.71% |
