Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 4101 | Thousand metric tons | NA |
| 2010 | 4220 | Thousand metric tons | 2.90% |
| 2011 | 4253 | Thousand metric tons | 0.78% |
| 2012 | 4196 | Thousand metric tons | -1.34% |
| 2013 | 4200 | Thousand metric tons | 0.10% |
