Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 688086 | Metric tons | NA |
| 2003 | 691380 | Metric tons | 0.48% |
| 2004 | 868574 | Metric tons | 25.63% |
| 2005 | 844369 | Metric tons | -2.79% |
| 2006 | 874601 | Metric tons | 3.58% |
| 2007 | 1018156 | Metric tons | 16.41% |
| 2008 | 1107789 | Metric tons | 8.80% |
| 2009 | 1113454 | Metric tons | 0.51% |
| 2010 | 1094123 | Metric tons | -1.74% |
| 2011 | 1094971 | Metric tons | 0.08% |
| 2012 | 1197560 | Metric tons | 9.37% |
