Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 157 | Thousand metric tons | NA |
| 2003 | 174 | Thousand metric tons | 10.83% |
| 2004 | 226 | Thousand metric tons | 29.89% |
| 2005 | 213 | Thousand metric tons | -5.75% |
| 2006 | 227 | Thousand metric tons | 6.57% |
| 2007 | 291 | Thousand metric tons | 28.19% |
| 2008 | 366 | Thousand metric tons | 25.77% |
| 2009 | 455.404998779297 | Thousand metric tons | 24.43% |
| 2010 | 512.642028808594 | Thousand metric tons | 12.57% |
| 2011 | 542 | Thousand metric tons | 5.73% |
| 2012 | 500 | Thousand metric tons | -7.75% |
