Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 13000 | Metric tons | NA |
| 2003 | 13500 | Metric tons | 3.85% |
| 2004 | 14000 | Metric tons | 3.70% |
| 2005 | 15000 | Metric tons | 7.14% |
| 2006 | 15000 | Metric tons | 0.00% |
| 2007 | 16000 | Metric tons | 6.67% |
| 2008 | 17500 | Metric tons | 9.38% |
| 2009 | 20000 | Metric tons | 14.29% |
| 2010 | 21000 | Metric tons | 5.00% |
| 2011 | 22000 | Metric tons | 4.76% |
| 2012 | 24000 | Metric tons | 9.09% |
| 2013 | 25000 | Metric tons | 4.17% |
