Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1147 | Thousand metric tons | NA |
| 2003 | 1328 | Thousand metric tons | 15.78% |
| 2004 | 1167 | Thousand metric tons | -12.12% |
| 2005 | 1243 | Thousand metric tons | 6.51% |
| 2006 | 1353 | Thousand metric tons | 8.85% |
| 2007 | 1581 | Thousand metric tons | 16.85% |
| 2008 | 1580 | Thousand metric tons | -0.06% |
| 2009 | 1277 | Thousand metric tons | -19.18% |
| 2010 | 1179 | Thousand metric tons | -7.67% |
| 2011 | 1225 | Thousand metric tons | 3.90% |
| 2012 | 1228 | Thousand metric tons | 0.24% |
| 2013 | 1270.13098144531 | Thousand metric tons | 3.43% |
