Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3290 | Thousand metric tons | NA |
| 2004 | 3141 | Thousand metric tons | -4.53% |
| 2005 | 3630 | Thousand metric tons | 15.57% |
| 2006 | 3580 | Thousand metric tons | -1.38% |
| 2007 | 4340 | Thousand metric tons | 21.23% |
| 2008 | 4970 | Thousand metric tons | 14.52% |
| 2009 | 5000 | Thousand metric tons | 0.60% |
| 2010 | 5500 | Thousand metric tons | 10.00% |
| 2011 | 5800 | Thousand metric tons | 5.45% |
| 2012 | 5700 | Thousand metric tons | -1.72% |
