Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 113.639999389648 | Thousand metric tons | NA |
| 2004 | 113.151000976563 | Thousand metric tons | -0.43 % |
| 2005 | 114.223999023438 | Thousand metric tons | 0.95 % |
| 2006 | 112.960998535156 | Thousand metric tons | -1.11 % |
| 2007 | 113.436996459961 | Thousand metric tons | 0.42 % |
| 2008 | 113 | Thousand metric tons | -0.39 % |
| 2009 | 50 | Thousand metric tons | -55.75 % |
