Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 4679 | Thousand metric tons | NA |
| 2003 | 4824 | Thousand metric tons | 3.10 % |
| 2004 | 4757 | Thousand metric tons | -1.39 % |
| 2005 | 4700 | Thousand metric tons | -1.20 % |
| 2006 | 4804 | Thousand metric tons | 2.21 % |
| 2007 | 5104 | Thousand metric tons | 6.24 % |
| 2008 | 5336 | Thousand metric tons | 4.55 % |
