Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 13079 | Thousand metric tons | NA |
| 2003 | 13416 | Thousand metric tons | 2.58% |
| 2004 | 13862.900390625 | Thousand metric tons | 3.33% |
| 2005 | 14179.400390625 | Thousand metric tons | 2.28% |
| 2006 | 14335.5 | Thousand metric tons | 1.10% |
| 2007 | 15077.599609375 | Thousand metric tons | 5.18% |
| 2008 | 13672 | Thousand metric tons | -9.32% |
| 2009 | 10985 | Thousand metric tons | -19.65% |
| 2010 | 12431 | Thousand metric tons | 13.16% |
| 2011 | 12001 | Thousand metric tons | -3.46% |
| 2012 | 12465 | Thousand metric tons | 3.87% |
