Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3290 | Thousand metric tons | NA |
| 2004 | 3141 | Thousand metric tons | -4.53 % |
| 2005 | 3630 | Thousand metric tons | 15.57 % |
| 2006 | 3580 | Thousand metric tons | -1.38 % |
| 2007 | 4340 | Thousand metric tons | 21.23 % |
| 2008 | 4970 | Thousand metric tons | 14.52 % |
| 2009 | 5000 | Thousand metric tons | 0.60 % |
