Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4183 | Thousand metric tons | NA |
| 2004 | 4278 | Thousand metric tons | 2.27% |
| 2005 | 4047 | Thousand metric tons | -5.40% |
| 2006 | 3800 | Thousand metric tons | -6.10% |
| 2007 | 4077 | Thousand metric tons | 7.29% |
| 2008 | 4670 | Thousand metric tons | 14.55% |
| 2009 | 3929 | Thousand metric tons | -15.87% |
| 2010 | 4720 | Thousand metric tons | 20.13% |
| 2011 | 4600 | Thousand metric tons | -2.54% |
| 2012 | 4762 | Thousand metric tons | 3.52% |
