Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 560 | Thousand metric tons | NA |
| 2004 | 683 | Thousand metric tons | 21.96 % |
| 2005 | 722 | Thousand metric tons | 5.71 % |
| 2006 | 861 | Thousand metric tons | 19.25 % |
| 2007 | 890 | Thousand metric tons | 3.37 % |
| 2008 | 947.7509765625 | Thousand metric tons | 6.49 % |
| 2009 | 1009.77197265625 | Thousand metric tons | 6.54 % |
