Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1333 | Thousand metric tons | NA |
| 2004 | 1351 | Thousand metric tons | 1.35% |
| 2005 | 1329 | Thousand metric tons | -1.63% |
| 2006 | 1335 | Thousand metric tons | 0.45% |
| 2007 | 1394 | Thousand metric tons | 4.42% |
| 2008 | 1289 | Thousand metric tons | -7.53% |
| 2009 | 1050 | Thousand metric tons | -18.54% |
| 2010 | 1325 | Thousand metric tons | 26.19% |
| 2011 | 1317 | Thousand metric tons | -0.60% |
| 2012 | 1229 | Thousand metric tons | -6.68% |
