Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 31009 | Thousand metric tons | NA |
| 2003 | 32749 | Thousand metric tons | 5.61 % |
| 2004 | 31854 | Thousand metric tons | -2.73 % |
| 2005 | 31009 | Thousand metric tons | -2.65 % |
| 2006 | 33630 | Thousand metric tons | 8.45 % |
| 2007 | 33382 | Thousand metric tons | -0.74 % |
| 2008 | 33581 | Thousand metric tons | 0.60 % |
