Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 847 | Thousand metric tons | NA |
| 2004 | 961 | Thousand metric tons | 13.46% |
| 2005 | 946 | Thousand metric tons | -1.56% |
| 2006 | 1104 | Thousand metric tons | 16.70% |
| 2007 | 1123 | Thousand metric tons | 1.72% |
| 2008 | 1082 | Thousand metric tons | -3.65% |
| 2009 | 867 | Thousand metric tons | -19.87% |
| 2010 | 986 | Thousand metric tons | 13.73% |
| 2011 | 971 | Thousand metric tons | -1.52% |
| 2012 | 1000 | Thousand metric tons | 2.99% |
| 2013 | 90 | Thousand metric tons | -91.00% |
