Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 16641 | Metric tons | NA |
| 2003 | 18000 | Metric tons | 8.17% |
| 2004 | 17700 | Metric tons | -1.67% |
| 2005 | 16400 | Metric tons | -7.34% |
| 2006 | 18000 | Metric tons | 9.76% |
| 2007 | 17600 | Metric tons | -2.22% |
| 2008 | 18800 | Metric tons | 6.82% |
| 2009 | 23233 | Metric tons | 23.58% |
| 2010 | 31062 | Metric tons | 33.70% |
| 2011 | 33597 | Metric tons | 8.16% |
| 2012 | 34000 | Metric tons | 1.20% |
