Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 7142 | Thousand metric tons | NA |
| 2003 | 8900 | Thousand metric tons | 24.61% |
| 2004 | 10635 | Thousand metric tons | 19.49% |
| 2005 | 12183 | Thousand metric tons | 14.56% |
| 2006 | 13732 | Thousand metric tons | 12.71% |
| 2007 | 15000 | Thousand metric tons | 9.23% |
| 2008 | 14918 | Thousand metric tons | -0.55% |
| 2009 | 9496 | Thousand metric tons | -36.35% |
| 2010 | 9457 | Thousand metric tons | -0.41% |
| 2011 | 10515 | Thousand metric tons | 11.19% |
| 2012 | 9801 | Thousand metric tons | -6.79% |
