Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 352.559997558594 | Thousand metric tons | NA |
| 2004 | 353.834991455078 | Thousand metric tons | 0.36% |
| 2005 | 360.161010742188 | Thousand metric tons | 1.79% |
| 2006 | 374.209991455078 | Thousand metric tons | 3.90% |
| 2007 | 386.597991943359 | Thousand metric tons | 3.31% |
| 2008 | 513.414978027344 | Thousand metric tons | 32.80% |
| 2009 | 404.903991699219 | Thousand metric tons | -21.14% |
| 2010 | 473.688995361328 | Thousand metric tons | 16.99% |
| 2011 | 499.052001953125 | Thousand metric tons | 5.35% |
| 2012 | 440 | Thousand metric tons | -11.83% |
| 2013 | 500 | Thousand metric tons | 13.64% |
