Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 294 | Metric tons | NA |
| 2003 | 307 | Metric tons | 4.42% |
| 2004 | 293 | Metric tons | -4.56% |
| 2005 | 309.899993896484 | Metric tons | 5.77% |
| 2006 | 268.200012207031 | Metric tons | -13.46% |
| 2007 | 270 | Metric tons | 0.67% |
| 2008 | 293.067993164063 | Metric tons | 8.54% |
| 2009 | 288.589996337891 | Metric tons | -1.53% |
| 2010 | 302.144989013672 | Metric tons | 4.70% |
| 2011 | 301.959014892578 | Metric tons | -0.06% |
| 2012 | 305 | Metric tons | 1.01% |
