Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 14282 | Thousand metric tons | NA |
| 2003 | 14638 | Thousand metric tons | 2.49% |
| 2004 | 15039 | Thousand metric tons | 2.74% |
| 2005 | 15166 | Thousand metric tons | 0.84% |
| 2006 | 15674 | Thousand metric tons | 3.35% |
| 2007 | 16666.666015625 | Thousand metric tons | 6.33% |
| 2008 | 12801 | Thousand metric tons | -23.19% |
| 2009 | 10069 | Thousand metric tons | -21.34% |
| 2010 | 8526 | Thousand metric tons | -15.32% |
| 2011 | 7418 | Thousand metric tons | -13.00% |
| 2012 | 7500 | Thousand metric tons | 1.11% |
