Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 16500 | Thousand metric tons | NA |
| 2010 | 17000 | Thousand metric tons | 3.03% |
| 2011 | 16000 | Thousand metric tons | -5.88% |
| 2012 | 17000 | Thousand metric tons | 6.25% |
| 2013 | 16000 | Thousand metric tons | -5.88% |
