Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 533 | Thousand metric tons | NA |
| 2003 | 757 | Thousand metric tons | 42.03% |
| 2004 | 870.099975585938 | Thousand metric tons | 14.94% |
| 2005 | 900 | Thousand metric tons | 3.44% |
| 2006 | 1210.59997558594 | Thousand metric tons | 34.51% |
| 2007 | 1300 | Thousand metric tons | 7.38% |
| 2008 | 1218 | Thousand metric tons | -6.31% |
| 2009 | 579 | Thousand metric tons | -52.46% |
| 2010 | 760 | Thousand metric tons | 31.26% |
| 2011 | 1015 | Thousand metric tons | 33.55% |
| 2012 | 1050 | Thousand metric tons | 3.45% |
