Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3320 | Thousand metric tons | NA |
| 2003 | 3830 | Thousand metric tons | 15.36% |
| 2004 | 5000 | Thousand metric tons | 30.55% |
| 2005 | 5083 | Thousand metric tons | 1.66% |
| 2006 | 4981 | Thousand metric tons | -2.01% |
| 2007 | 5000 | Thousand metric tons | 0.38% |
| 2008 | 4493 | Thousand metric tons | -10.14% |
| 2009 | 2797 | Thousand metric tons | -37.75% |
| 2010 | 2379 | Thousand metric tons | -14.94% |
| 2011 | 2103 | Thousand metric tons | -11.60% |
| 2012 | 2600 | Thousand metric tons | 23.63% |
