Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5632 | Thousand metric tons | NA |
| 2004 | 6399 | Thousand metric tons | 13.62% |
| 2005 | 4477 | Thousand metric tons | -30.04% |
| 2006 | 5332.6318359375 | Thousand metric tons | 19.11% |
| 2007 | 5804.41796875 | Thousand metric tons | 8.85% |
| 2008 | 4933.78076171875 | Thousand metric tons | -15.00% |
| 2009 | 2983.5 | Thousand metric tons | -39.53% |
| 2010 | 3638 | Thousand metric tons | 21.94% |
| 2011 | 3974.92993164063 | Thousand metric tons | 9.26% |
| 2012 | 3952 | Thousand metric tons | -0.58% |
