Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 380 | Thousand metric tons | NA |
| 2004 | 390 | Thousand metric tons | 2.63% |
| 2005 | 410 | Thousand metric tons | 5.13% |
| 2006 | 420 | Thousand metric tons | 2.44% |
| 2007 | 420 | Thousand metric tons | 0.00% |
| 2008 | 440 | Thousand metric tons | 4.76% |
| 2009 | 440 | Thousand metric tons | 0.00% |
| 2010 | 400 | Thousand metric tons | -9.09% |
| 2011 | 440 | Thousand metric tons | 10.00% |
| 2012 | 420 | Thousand metric tons | -4.55% |
