Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6234 | Thousand metric tons | NA |
| 2004 | 6011 | Thousand metric tons | -3.58 % |
| 2005 | 6130 | Thousand metric tons | 1.98 % |
| 2006 | 6159 | Thousand metric tons | 0.47 % |
| 2007 | 5358 | Thousand metric tons | -13.01 % |
| 2008 | 5350 | Thousand metric tons | -0.15 % |
| 2009 | 4376 | Thousand metric tons | -18.21 % |
