Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 2400 | Thousand metric tons | NA |
| 2004 | 2600 | Thousand metric tons | 8.33% |
| 2005 | 2600 | Thousand metric tons | 0.00% |
| 2006 | 2800 | Thousand metric tons | 7.69% |
| 2007 | 2900 | Thousand metric tons | 3.57% |
| 2008 | 2800 | Thousand metric tons | -3.45% |
| 2009 | 2322 | Thousand metric tons | -17.07% |
| 2010 | 2670 | Thousand metric tons | 14.99% |
| 2011 | 2822 | Thousand metric tons | 5.69% |
| 2012 | 2807 | Thousand metric tons | -0.53% |
| 2013 | 2810 | Thousand metric tons | 0.11% |
