Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6645.255859375 | Thousand metric tons | NA |
| 2004 | 7800 | Thousand metric tons | 17.38 % |
| 2005 | 8897 | Thousand metric tons | 14.06 % |
| 2006 | 8400 | Thousand metric tons | -5.59 % |
| 2007 | 7782 | Thousand metric tons | -7.36 % |
| 2008 | 7140 | Thousand metric tons | -8.25 % |
| 2009 | 7150 | Thousand metric tons | 0.14 % |
