Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 422 | Thousand metric tons | NA |
| 2003 | 394 | Thousand metric tons | -6.64% |
| 2004 | 452.27099609375 | Thousand metric tons | 14.79% |
| 2005 | 547.580993652344 | Thousand metric tons | 21.07% |
| 2006 | 554.02001953125 | Thousand metric tons | 1.18% |
| 2007 | 627.377014160156 | Thousand metric tons | 13.24% |
| 2008 | 571.343017578125 | Thousand metric tons | -8.93% |
| 2009 | 597.570983886719 | Thousand metric tons | 4.59% |
| 2010 | 513.309997558594 | Thousand metric tons | -14.10% |
| 2011 | 476.118011474609 | Thousand metric tons | -7.25% |
| 2012 | 558.242004394531 | Thousand metric tons | 17.25% |
| 2013 | 557.448974609375 | Thousand metric tons | -0.14% |
