Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 17363 | Thousand metric tons | NA |
| 2004 | 20950 | Thousand metric tons | 20.66% |
| 2005 | 22034 | Thousand metric tons | 5.17% |
| 2006 | 23236.30078125 | Thousand metric tons | 5.46% |
| 2007 | 25460.69921875 | Thousand metric tons | 9.57% |
| 2008 | 28097.5 | Thousand metric tons | 10.36% |
| 2009 | 28200 | Thousand metric tons | 0.36% |
