Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 900 | Thousand metric tons | NA |
| 2004 | 900 | Thousand metric tons | 0.00% |
| 2005 | 807 | Thousand metric tons | -10.33% |
| 2006 | 773 | Thousand metric tons | -4.21% |
| 2007 | 850 | Thousand metric tons | 9.96% |
| 2008 | 702 | Thousand metric tons | -17.41% |
| 2009 | 1364 | Thousand metric tons | 94.30% |
| 2010 | 1361 | Thousand metric tons | -0.22% |
| 2011 | 1371 | Thousand metric tons | 0.73% |
| 2012 | 1340 | Thousand metric tons | -2.26% |
| 2013 | 1274 | Thousand metric tons | -4.93% |
