Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 695000 | Metric tons | NA |
| 2003 | 675000 | Metric tons | -2.88 % |
| 2004 | 675000 | Metric tons | 0.00 % |
| 2005 | 700000 | Metric tons | 3.70 % |
| 2006 | 725000 | Metric tons | 3.57 % |
| 2007 | 740000 | Metric tons | 2.07 % |
| 2008 | 750000 | Metric tons | 1.35 % |
