Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6116 | Thousand metric tons | NA |
| 2004 | 5735 | Thousand metric tons | -6.23 % |
| 2005 | 6203 | Thousand metric tons | 8.16 % |
| 2006 | 6276 | Thousand metric tons | 1.18 % |
| 2007 | 6351 | Thousand metric tons | 1.20 % |
| 2008 | 6409 | Thousand metric tons | 0.91 % |
| 2009 | 4400 | Thousand metric tons | -31.35 % |
