Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 31679 | Thousand metric tons | NA |
| 2003 | 32530 | Thousand metric tons | 2.69 % |
| 2004 | 35626 | Thousand metric tons | 9.52 % |
| 2005 | 37872 | Thousand metric tons | 6.30 % |
| 2006 | 39408 | Thousand metric tons | 4.06 % |
| 2007 | 35668 | Thousand metric tons | -9.49 % |
| 2008 | 35600 | Thousand metric tons | -0.19 % |
