Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 2275 | Thousand metric tons | NA |
| 2004 | 2336.5 | Thousand metric tons | 2.70% |
| 2005 | 2055 | Thousand metric tons | -12.05% |
| 2006 | 2072 | Thousand metric tons | 0.83% |
| 2007 | 2065 | Thousand metric tons | -0.34% |
| 2008 | 1600 | Thousand metric tons | -22.52% |
| 2009 | 1182 | Thousand metric tons | -26.13% |
| 2010 | 1752 | Thousand metric tons | 48.22% |
| 2011 | 1915 | Thousand metric tons | 9.30% |
| 2012 | 1699 | Thousand metric tons | -11.28% |
