Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 13800 | Metric tons | NA |
| 2010 | 13000 | Metric tons | -5.80% |
| 2011 | 13300 | Metric tons | 2.31% |
| 2012 | 13600 | Metric tons | 2.26% |
| 2013 | 13800 | Metric tons | 1.47% |
