Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 7813 | Thousand metric tons | NA |
| 2004 | 8224 | Thousand metric tons | 5.26% |
| 2005 | 7254 | Thousand metric tons | -11.79% |
| 2006 | 7516 | Thousand metric tons | 3.61% |
| 2007 | 6576 | Thousand metric tons | -12.51% |
| 2008 | 7125 | Thousand metric tons | 8.35% |
| 2009 | 3087 | Thousand metric tons | -56.67% |
| 2010 | 4688 | Thousand metric tons | 51.86% |
| 2011 | 4725 | Thousand metric tons | 0.79% |
| 2012 | 4072 | Thousand metric tons | -13.82% |
