Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 15580 | Metric tons | NA |
| 2004 | 14931 | Metric tons | -4.17 % |
| 2005 | 15346 | Metric tons | 2.78 % |
| 2006 | 16494 | Metric tons | 7.48 % |
| 2007 | 15473 | Metric tons | -6.19 % |
| 2008 | 15503 | Metric tons | 0.19 % |
| 2009 | 17399 | Metric tons | 12.23 % |
| 2010 | 15793 | Metric tons | -9.23 % |
| 2011 | 16000 | Metric tons | 1.31 % |
| 2012 | 17494 | Metric tons | 9.34 % |
| 2013 | 20656 | Metric tons | 18.07 % |
