Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 130 | Thousand metric tons | NA |
| 2004 | 135 | Thousand metric tons | 3.85 % |
| 2005 | 140 | Thousand metric tons | 3.70 % |
| 2006 | 145 | Thousand metric tons | 3.57 % |
| 2007 | 145 | Thousand metric tons | 0.00 % |
| 2008 | 140 | Thousand metric tons | -3.45 % |
| 2009 | 145 | Thousand metric tons | 3.57 % |
