Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2005 | 68854 | Metric tons | NA |
| 2006 | 71056 | Metric tons | 3.20% |
| 2007 | 68000 | Metric tons | -4.30% |
| 2008 | 68000 | Metric tons | 0.00% |
| 2009 | 61715 | Metric tons | -9.24% |
| 2010 | 51659 | Metric tons | -16.29% |
| 2011 | 44400 | Metric tons | -14.05% |
| 2012 | 39605 | Metric tons | -10.80% |
| 2013 | 53394 | Metric tons | 34.82% |
