Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 28600 | Thousand metric tons | NA |
| 2003 | 30460 | Thousand metric tons | 6.50 % |
| 2004 | 32198 | Thousand metric tons | 5.71 % |
| 2005 | 32650 | Thousand metric tons | 1.40 % |
| 2006 | 35300 | Thousand metric tons | 8.12 % |
| 2007 | 40000 | Thousand metric tons | 13.31 % |
| 2008 | 44400 | Thousand metric tons | 11.00 % |
