Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 41722 | Thousand metric tons | NA |
| 2003 | 43580 | Thousand metric tons | 4.45% |
| 2004 | 45343 | Thousand metric tons | 4.05% |
| 2005 | 40284 | Thousand metric tons | -11.16% |
| 2006 | 47814 | Thousand metric tons | 18.69% |
| 2007 | 47541.63671875 | Thousand metric tons | -0.57% |
| 2008 | 43030 | Thousand metric tons | -9.49% |
| 2009 | 36317 | Thousand metric tons | -15.60% |
| 2010 | 34408 | Thousand metric tons | -5.26% |
| 2011 | 33120 | Thousand metric tons | -3.74% |
| 2012 | 33000 | Thousand metric tons | -0.36% |
