Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 4289 | Thousand metric tons | NA |
| 2010 | 4350 | Thousand metric tons | 1.42% |
| 2011 | 4371 | Thousand metric tons | 0.48% |
| 2012 | 4385 | Thousand metric tons | 0.32% |
| 2013 | 4440 | Thousand metric tons | 1.25% |
