Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 7953 | Thousand metric tons | NA |
| 2004 | 8162 | Thousand metric tons | 2.63% |
| 2005 | 7681 | Thousand metric tons | -5.89% |
| 2006 | 7703 | Thousand metric tons | 0.29% |
| 2007 | 8382 | Thousand metric tons | 8.81% |
| 2008 | 8186 | Thousand metric tons | -2.34% |
| 2009 | 6453 | Thousand metric tons | -21.17% |
| 2010 | 7234 | Thousand metric tons | 12.10% |
| 2011 | 7770 | Thousand metric tons | 7.41% |
| 2012 | 7498 | Thousand metric tons | -3.50% |
| 2013 | 7500 | Thousand metric tons | 0.03% |
