Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 402 | Thousand metric tons | NA |
| 2003 | 424 | Thousand metric tons | 5.47 % |
| 2004 | 467.065002441406 | Thousand metric tons | 10.16 % |
| 2005 | 552.495971679688 | Thousand metric tons | 18.29 % |
| 2006 | 649.943969726563 | Thousand metric tons | 17.64 % |
| 2007 | 620 | Thousand metric tons | -4.61 % |
| 2008 | 640 | Thousand metric tons | 3.23 % |
