Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1341 | Thousand metric tons | NA |
| 2004 | 1347 | Thousand metric tons | 0.45% |
| 2005 | 1304 | Thousand metric tons | -3.19% |
| 2006 | 1245 | Thousand metric tons | -4.52% |
| 2007 | 1282 | Thousand metric tons | 2.97% |
| 2008 | 1151 | Thousand metric tons | -10.22% |
| 2009 | 1214 | Thousand metric tons | 5.47% |
| 2010 | 1286 | Thousand metric tons | 5.93% |
| 2011 | 1139 | Thousand metric tons | -11.43% |
| 2012 | 1277 | Thousand metric tons | 12.12% |
| 2013 | 1295 | Thousand metric tons | 1.41% |
