Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4.57999992370605 | Thousand metric tons | NA |
| 2004 | 4.64300012588501 | Thousand metric tons | 1.38% |
| 2005 | 4.87099981307983 | Thousand metric tons | 4.91% |
| 2006 | 9.76200008392334 | Thousand metric tons | 100.41% |
| 2007 | 7.48899984359741 | Thousand metric tons | -23.28% |
| 2008 | 9.76399993896484 | Thousand metric tons | 30.38% |
| 2009 | 11.3520002365112 | Thousand metric tons | 16.26% |
| 2010 | 13.1110000610352 | Thousand metric tons | 15.50% |
| 2011 | 8 | Thousand metric tons | -38.98% |
| 2012 | 20 | Thousand metric tons | 150.00% |
| 2013 | 19 | Thousand metric tons | -5.00% |
