Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 1200 | Thousand metric tons | NA |
| 2010 | 1122 | Thousand metric tons | -6.50% |
| 2011 | 978 | Thousand metric tons | -12.83% |
| 2012 | 925 | Thousand metric tons | -5.42% |
| 2013 | 1000 | Thousand metric tons | 8.11% |
