Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 13400 | Thousand metric tons | NA |
| 2003 | 13060 | Thousand metric tons | -2.54% |
| 2004 | 13346 | Thousand metric tons | 2.19% |
| 2005 | 15494 | Thousand metric tons | 16.09% |
| 2006 | 12033 | Thousand metric tons | -22.34% |
| 2007 | 13048 | Thousand metric tons | 8.44% |
| 2008 | 13369 | Thousand metric tons | 2.46% |
| 2009 | 14865 | Thousand metric tons | 11.19% |
| 2010 | 15900 | Thousand metric tons | 6.96% |
| 2011 | 16063 | Thousand metric tons | 1.03% |
| 2012 | 18907 | Thousand metric tons | 17.71% |
