Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 57000 | Metric tons | NA |
| 2004 | 61000 | Metric tons | 7.02% |
| 2005 | 62000 | Metric tons | 1.64% |
| 2006 | 50000 | Metric tons | -19.35% |
| 2007 | 55000 | Metric tons | 10.00% |
| 2008 | 43000 | Metric tons | -21.82% |
| 2009 | 36000 | Metric tons | -16.28% |
| 2010 | 33000 | Metric tons | -8.33% |
| 2011 | 31000 | Metric tons | -6.06% |
| 2012 | 31000 | Metric tons | 0.00% |
