Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 6740 | Thousand metric tons | NA |
| 2003 | 6986 | Thousand metric tons | 3.65 % |
| 2004 | 9221.4580078125 | Thousand metric tons | 32.00 % |
| 2005 | 6251.96923828125 | Thousand metric tons | -32.20 % |
| 2006 | 6075.89306640625 | Thousand metric tons | -2.82 % |
| 2007 | 6080 | Thousand metric tons | 0.07 % |
| 2008 | 5135.15087890625 | Thousand metric tons | -15.54 % |
