Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 195 | Thousand metric tons | NA |
| 2004 | 205.100006103516 | Thousand metric tons | 5.18% |
| 2005 | 215.399993896484 | Thousand metric tons | 5.02% |
| 2006 | 215.5 | Thousand metric tons | 0.05% |
| 2007 | 215 | Thousand metric tons | -0.23% |
| 2008 | 215 | Thousand metric tons | 0.00% |
| 2009 | 216 | Thousand metric tons | 0.47% |
| 2010 | 216 | Thousand metric tons | 0.00% |
| 2011 | 216 | Thousand metric tons | 0.00% |
| 2012 | 220 | Thousand metric tons | 1.85% |
| 2013 | 225 | Thousand metric tons | 2.27% |
