Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4215.10009765625 | Thousand metric tons | NA |
| 2004 | 4051.69995117188 | Thousand metric tons | -3.88% |
| 2005 | 4757 | Thousand metric tons | 17.41% |
| 2006 | 4924 | Thousand metric tons | 3.51% |
| 2007 | 5054 | Thousand metric tons | 2.64% |
| 2008 | 5200 | Thousand metric tons | 2.89% |
| 2009 | 4000 | Thousand metric tons | -23.08% |
