Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 382.269989013672 | Thousand metric tons | NA |
| 2010 | 222.509002685547 | Thousand metric tons | -41.79% |
| 2011 | 372.230010986328 | Thousand metric tons | 67.29% |
| 2012 | 308.846984863281 | Thousand metric tons | -17.03% |
| 2013 | 300 | Thousand metric tons | -2.86% |
