Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1230 | Thousand metric tons | NA |
| 2004 | 1470 | Thousand metric tons | 19.51% |
| 2005 | 1390 | Thousand metric tons | -5.44% |
| 2006 | 1290 | Thousand metric tons | -7.19% |
| 2007 | 1420 | Thousand metric tons | 10.08% |
| 2008 | 1290 | Thousand metric tons | -9.15% |
| 2009 | 1230 | Thousand metric tons | -4.65% |
| 2010 | 1360 | Thousand metric tons | 10.57% |
| 2011 | 1200 | Thousand metric tons | -11.76% |
| 2012 | 1300 | Thousand metric tons | 8.33% |
