Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5207 | Thousand metric tons | NA |
| 2004 | 5384 | Thousand metric tons | 3.40% |
| 2005 | 4627 | Thousand metric tons | -14.06% |
| 2006 | 5191 | Thousand metric tons | 12.19% |
| 2007 | 5288.7001953125 | Thousand metric tons | 1.88% |
| 2008 | 4737 | Thousand metric tons | -10.43% |
| 2009 | 3483 | Thousand metric tons | -26.47% |
| 2010 | 3987 | Thousand metric tons | 14.47% |
| 2011 | 4137.07421875 | Thousand metric tons | 3.76% |
| 2012 | 3935.7890625 | Thousand metric tons | -4.87% |
