Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 3471 | Thousand metric tons | NA |
| 2010 | 4006 | Thousand metric tons | 15.41% |
| 2011 | 2912 | Thousand metric tons | -27.31% |
| 2012 | 3098 | Thousand metric tons | 6.39% |
| 2013 | 2200 | Thousand metric tons | -28.99% |
