Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2004 | 12000 | Metric tons | NA |
| 2005 | 12900 | Metric tons | 7.50% |
| 2006 | 12000 | Metric tons | -6.98% |
| 2007 | 16500 | Metric tons | 37.50% |
| 2008 | 20800 | Metric tons | 26.06% |
| 2009 | 23400 | Metric tons | 12.50% |
| 2010 | 24600 | Metric tons | 5.13% |
| 2011 | 28000 | Metric tons | 13.82% |
| 2012 | 34400 | Metric tons | 22.86% |
