Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 19200 | Thousand metric tons | NA |
| 2004 | 20000 | Thousand metric tons | 4.17 % |
| 2005 | 20000 | Thousand metric tons | 0.00 % |
| 2006 | 21000 | Thousand metric tons | 5.00 % |
| 2007 | 20200 | Thousand metric tons | -3.81 % |
| 2008 | 19900 | Thousand metric tons | -1.49 % |
| 2009 | 15800 | Thousand metric tons | -20.60 % |
