Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 15242 | Metric tons | NA |
| 2003 | 16755 | Metric tons | 9.93 % |
| 2004 | 17569 | Metric tons | 4.86 % |
| 2005 | 18433 | Metric tons | 4.92 % |
| 2006 | 18444 | Metric tons | 0.06 % |
| 2007 | 15972 | Metric tons | -13.40 % |
| 2008 | 17320 | Metric tons | 8.44 % |
| 2009 | 19273 | Metric tons | 11.28 % |
