Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1000 | Thousand metric tons | NA |
| 2004 | 1500 | Thousand metric tons | 50.00% |
| 2005 | 1600 | Thousand metric tons | 6.67% |
| 2006 | 1400 | Thousand metric tons | -12.50% |
| 2007 | 1300 | Thousand metric tons | -7.14% |
| 2008 | 1300 | Thousand metric tons | 0.00% |
| 2009 | 1200 | Thousand metric tons | -7.69% |
| 2010 | 1258 | Thousand metric tons | 4.83% |
| 2011 | 1337 | Thousand metric tons | 6.28% |
| 2012 | 1400 | Thousand metric tons | 4.71% |
| 2013 | 1500 | Thousand metric tons | 7.14% |
