Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 40000 | Metric tons | NA |
| 2003 | 43000 | Metric tons | 7.50% |
| 2004 | 45000 | Metric tons | 4.65% |
| 2005 | 45000 | Metric tons | 0.00% |
| 2006 | 35000 | Metric tons | -22.22% |
| 2007 | 37000 | Metric tons | 5.71% |
| 2008 | 37000 | Metric tons | 0.00% |
| 2009 | 29000 | Metric tons | -21.62% |
| 2010 | 29000 | Metric tons | 0.00% |
| 2011 | 29000 | Metric tons | 0.00% |
| 2012 | 20000 | Metric tons | -31.03% |
| 2013 | 32000 | Metric tons | 60.00% |
