Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6524 | Metric tons | NA |
| 2004 | 7264 | Metric tons | 11.34% |
| 2005 | 8095 | Metric tons | 11.44% |
| 2006 | 8724 | Metric tons | 7.77% |
| 2007 | 9282 | Metric tons | 6.40% |
| 2008 | 9500 | Metric tons | 2.35% |
| 2009 | 8232 | Metric tons | -13.35% |
| 2010 | 9216 | Metric tons | 11.95% |
| 2011 | 9277 | Metric tons | 0.66% |
| 2012 | 9315 | Metric tons | 0.41% |
| 2013 | 9500 | Metric tons | 1.99% |
