Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 7000 | Thousand metric tons | NA |
| 2003 | 8000 | Thousand metric tons | 14.29% |
| 2004 | 9000 | Thousand metric tons | 12.50% |
| 2005 | 9800 | Thousand metric tons | 8.89% |
| 2006 | 12600 | Thousand metric tons | 28.57% |
| 2007 | 14000 | Thousand metric tons | 11.11% |
| 2008 | 21885 | Thousand metric tons | 56.32% |
| 2009 | 18997 | Thousand metric tons | -13.20% |
| 2010 | 18000 | Thousand metric tons | -5.25% |
| 2011 | 18000 | Thousand metric tons | 0.00% |
| 2012 | 17000 | Thousand metric tons | -5.56% |
