Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1964.96496582031 | Thousand metric tons | NA |
| 2004 | 1880.09301757813 | Thousand metric tons | -4.32% |
| 2005 | 1900 | Thousand metric tons | 1.06% |
| 2006 | 1900 | Thousand metric tons | 0.00% |
| 2007 | 2000 | Thousand metric tons | 5.26% |
| 2008 | 2000 | Thousand metric tons | 0.00% |
| 2009 | 1500 | Thousand metric tons | -25.00% |
