Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 166 | Thousand metric tons | NA |
| 2003 | 150 | Thousand metric tons | -9.64% |
| 2004 | 148 | Thousand metric tons | -1.33% |
| 2005 | 196.132995605469 | Thousand metric tons | 32.52% |
| 2006 | 170.350997924805 | Thousand metric tons | -13.15% |
| 2007 | 170 | Thousand metric tons | -0.21% |
| 2008 | 170 | Thousand metric tons | 0.00% |
| 2009 | 221.888000488281 | Thousand metric tons | 30.52% |
| 2010 | 197.606002807617 | Thousand metric tons | -10.94% |
| 2011 | 167.518005371094 | Thousand metric tons | -15.23% |
| 2012 | 182.557006835938 | Thousand metric tons | 8.98% |
| 2013 | 114.449996948242 | Thousand metric tons | -37.31% |
