Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 31500 | Metric tons | NA |
| 2003 | 28500 | Metric tons | -9.52 % |
| 2004 | 29500 | Metric tons | 3.51 % |
| 2005 | 26900 | Metric tons | -8.81 % |
| 2006 | 27400 | Metric tons | 1.86 % |
| 2007 | 33900 | Metric tons | 23.72 % |
| 2008 | 28000 | Metric tons | -17.40 % |
