Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 28.4440002441406 | Thousand metric tons | NA |
| 2010 | 34.4550018310547 | Thousand metric tons | 21.13% |
| 2011 | 32.2970008850098 | Thousand metric tons | -6.26% |
| 2012 | 34.015998840332 | Thousand metric tons | 5.32% |
| 2013 | 34 | Thousand metric tons | -0.05% |
