Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 38815 | Metric tons | NA |
| 2003 | 40202 | Metric tons | 3.57% |
| 2004 | 67675 | Metric tons | 68.34% |
| 2005 | 42145 | Metric tons | -37.72% |
| 2006 | 38470 | Metric tons | -8.72% |
| 2007 | 39019 | Metric tons | 1.43% |
| 2008 | 39037 | Metric tons | 0.05% |
| 2009 | 37503 | Metric tons | -3.93% |
| 2010 | 33848 | Metric tons | -9.75% |
| 2011 | 28882 | Metric tons | -14.67% |
| 2012 | 26105 | Metric tons | -9.61% |
| 2013 | 23668 | Metric tons | -9.34% |
