Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 182.477005004883 | Thousand metric tons | NA |
| 2004 | 212.602005004883 | Thousand metric tons | 16.51% |
| 2005 | 220 | Thousand metric tons | 3.48% |
| 2006 | 205 | Thousand metric tons | -6.82% |
| 2007 | 215.981002807617 | Thousand metric tons | 5.36% |
| 2008 | 248 | Thousand metric tons | 14.82% |
| 2009 | 200 | Thousand metric tons | -19.35% |
| 2010 | 192 | Thousand metric tons | -4.00% |
| 2011 | 223.554000854492 | Thousand metric tons | 16.43% |
| 2012 | 230 | Thousand metric tons | 2.88% |
| 2013 | 300 | Thousand metric tons | 30.43% |
