Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 12700 | Thousand metric tons | NA |
| 2004 | 12800 | Thousand metric tons | 0.79 % |
| 2005 | 14400 | Thousand metric tons | 12.50 % |
| 2006 | 13800 | Thousand metric tons | -4.17 % |
| 2007 | 13800 | Thousand metric tons | 0.00 % |
| 2008 | 13800 | Thousand metric tons | 0.00 % |
| 2009 | 19759 | Thousand metric tons | 43.18 % |
| 2010 | 17656 | Thousand metric tons | -10.64 % |
| 2011 | 16369 | Thousand metric tons | -7.29 % |
| 2012 | 13946 | Thousand metric tons | -14.80 % |
| 2013 | 13870 | Thousand metric tons | -0.54 % |
