Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 9759 | Thousand metric tons | NA |
| 2003 | 8567 | Thousand metric tons | -12.21% |
| 2004 | 8843 | Thousand metric tons | 3.22% |
| 2005 | 8438 | Thousand metric tons | -4.58% |
| 2006 | 8340 | Thousand metric tons | -1.16% |
| 2007 | 12631 | Thousand metric tons | 51.45% |
| 2008 | 6629 | Thousand metric tons | -47.52% |
| 2009 | 5318 | Thousand metric tons | -19.78% |
| 2010 | 4587 | Thousand metric tons | -13.75% |
| 2011 | 5069 | Thousand metric tons | 10.51% |
| 2012 | 6000 | Thousand metric tons | 18.37% |
