Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 7953 | Thousand metric tons | NA |
| 2004 | 8506.94140625 | Thousand metric tons | 6.97% |
| 2005 | 8879.197265625 | Thousand metric tons | 4.38% |
| 2006 | 9014.2724609375 | Thousand metric tons | 1.52% |
| 2007 | 9359 | Thousand metric tons | 3.82% |
| 2008 | 9528 | Thousand metric tons | 1.81% |
| 2009 | 6746 | Thousand metric tons | -29.20% |
| 2010 | 8547 | Thousand metric tons | 26.70% |
| 2011 | 8005 | Thousand metric tons | -6.34% |
| 2012 | 7581 | Thousand metric tons | -5.30% |
| 2013 | 7600 | Thousand metric tons | 0.25% |
