Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 9553 | Thousand metric tons | NA |
| 2003 | 10377 | Thousand metric tons | 8.63% |
| 2004 | 10674 | Thousand metric tons | 2.86% |
| 2005 | 11133 | Thousand metric tons | 4.30% |
| 2006 | 10658 | Thousand metric tons | -4.27% |
| 2007 | 11817 | Thousand metric tons | 10.87% |
| 2008 | 11296 | Thousand metric tons | -4.41% |
| 2009 | 10524 | Thousand metric tons | -6.83% |
| 2010 | 11534 | Thousand metric tons | 9.60% |
| 2011 | 11160 | Thousand metric tons | -3.24% |
| 2012 | 12000 | Thousand metric tons | 7.53% |
