Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1206 | Thousand metric tons | NA |
| 2003 | 1189 | Thousand metric tons | -1.41 % |
| 2004 | 1039.39099121094 | Thousand metric tons | -12.58 % |
| 2005 | 1005.33001708984 | Thousand metric tons | -3.28 % |
| 2006 | 1010 | Thousand metric tons | 0.46 % |
| 2007 | 1000 | Thousand metric tons | -0.99 % |
| 2008 | 1000 | Thousand metric tons | 0.00 % |
