Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 9941 | Thousand metric tons | NA |
| 2003 | 11265 | Thousand metric tons | 13.32 % |
| 2004 | 11483 | Thousand metric tons | 1.94 % |
| 2005 | 11687 | Thousand metric tons | 1.78 % |
| 2006 | 10983 | Thousand metric tons | -6.02 % |
| 2007 | 10916.4365234375 | Thousand metric tons | -0.61 % |
| 2008 | 11688.107421875 | Thousand metric tons | 7.07 % |
| 2009 | 11600 | Thousand metric tons | -0.75 % |
