Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 666 | Thousand metric tons | NA |
| 2004 | 647 | Thousand metric tons | -2.85% |
| 2005 | 535 | Thousand metric tons | -17.31% |
| 2006 | 538.299987792969 | Thousand metric tons | 0.62% |
| 2007 | 546.400024414063 | Thousand metric tons | 1.50% |
| 2008 | 511 | Thousand metric tons | -6.48% |
| 2009 | 317 | Thousand metric tons | -37.96% |
