Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 494.716003417969 | Thousand metric tons | NA |
| 2004 | 498.059997558594 | Thousand metric tons | 0.68% |
| 2005 | 607 | Thousand metric tons | 21.87% |
| 2006 | 842 | Thousand metric tons | 38.71% |
| 2007 | 748.231994628906 | Thousand metric tons | -11.14% |
| 2008 | 796 | Thousand metric tons | 6.38% |
| 2009 | 440 | Thousand metric tons | -44.72% |
