Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1581 | Thousand metric tons | NA |
| 2004 | 1690 | Thousand metric tons | 6.89% |
| 2005 | 1466 | Thousand metric tons | -13.25% |
| 2006 | 2146 | Thousand metric tons | 46.38% |
| 2007 | 1987 | Thousand metric tons | -7.41% |
| 2008 | 1979 | Thousand metric tons | -0.40% |
| 2009 | 1296 | Thousand metric tons | -34.51% |
| 2010 | 1171 | Thousand metric tons | -9.65% |
| 2011 | 1431 | Thousand metric tons | 22.20% |
| 2012 | 1593 | Thousand metric tons | 11.32% |
| 2013 | 1690 | Thousand metric tons | 6.09% |
