Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 250 | Thousand metric tons | NA |
| 2004 | 300 | Thousand metric tons | 20.00% |
| 2005 | 130.888000488281 | Thousand metric tons | -56.37% |
| 2006 | 139.888000488281 | Thousand metric tons | 6.88% |
| 2007 | 147.854995727539 | Thousand metric tons | 5.70% |
| 2008 | 150 | Thousand metric tons | 1.45% |
| 2009 | 278.230987548828 | Thousand metric tons | 85.49% |
| 2010 | 240.919006347656 | Thousand metric tons | -13.41% |
| 2011 | 227.436996459961 | Thousand metric tons | -5.60% |
| 2012 | 106.276000976563 | Thousand metric tons | -53.27% |
| 2013 | 102.069999694824 | Thousand metric tons | -3.96% |
