Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 20300 | Thousand metric tons | NA |
| 2003 | 21500 | Thousand metric tons | 5.91 % |
| 2004 | 22300 | Thousand metric tons | 3.72 % |
| 2005 | 23300 | Thousand metric tons | 4.48 % |
| 2006 | 23300 | Thousand metric tons | 0.00 % |
| 2007 | 24700 | Thousand metric tons | 6.01 % |
| 2008 | 23800 | Thousand metric tons | -3.64 % |
| 2009 | 17700 | Thousand metric tons | -25.63 % |
