Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 11336 | Thousand metric tons | NA |
| 2004 | 13024 | Thousand metric tons | 14.89% |
| 2005 | 14210 | Thousand metric tons | 9.11% |
| 2006 | 15600 | Thousand metric tons | 9.78% |
| 2007 | 17720 | Thousand metric tons | 13.59% |
| 2008 | 18540 | Thousand metric tons | 4.63% |
| 2009 | 19450 | Thousand metric tons | 4.91% |
| 2010 | 20350 | Thousand metric tons | 4.63% |
| 2011 | 22940 | Thousand metric tons | 12.73% |
| 2012 | 24010 | Thousand metric tons | 4.66% |
| 2013 | 24290 | Thousand metric tons | 1.17% |
