Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3911 | Thousand metric tons | NA |
| 2003 | 5217 | Thousand metric tons | 33.39% |
| 2004 | 6254.06494140625 | Thousand metric tons | 19.88% |
| 2005 | 7594.5068359375 | Thousand metric tons | 21.43% |
| 2006 | 8929.3759765625 | Thousand metric tons | 17.58% |
| 2007 | 9602.25 | Thousand metric tons | 7.54% |
| 2008 | 9703 | Thousand metric tons | 1.05% |
| 2009 | 9385 | Thousand metric tons | -3.28% |
| 2010 | 10423 | Thousand metric tons | 11.06% |
| 2011 | 11592 | Thousand metric tons | 11.22% |
| 2012 | 10716 | Thousand metric tons | -7.56% |
