Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 71828 | Thousand metric tons | NA |
| 2003 | 68766 | Thousand metric tons | -4.26% |
| 2004 | 67376 | Thousand metric tons | -2.02% |
| 2005 | 69629 | Thousand metric tons | 3.34% |
| 2006 | 69942 | Thousand metric tons | 0.45% |
| 2007 | 67685 | Thousand metric tons | -3.23% |
| 2008 | 62810 | Thousand metric tons | -7.20% |
| 2009 | 54800 | Thousand metric tons | -12.75% |
| 2010 | 51526 | Thousand metric tons | -5.97% |
| 2011 | 51291 | Thousand metric tons | -0.46% |
| 2012 | 54737 | Thousand metric tons | 6.72% |
