Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2137 | Thousand metric tons | NA |
| 2003 | 2100 | Thousand metric tons | -1.73 % |
| 2004 | 2938.8701171875 | Thousand metric tons | 39.95 % |
| 2005 | 3618.22094726563 | Thousand metric tons | 23.12 % |
| 2006 | 4092.69189453125 | Thousand metric tons | 13.11 % |
| 2007 | 4413.34619140625 | Thousand metric tons | 7.83 % |
| 2008 | 4400 | Thousand metric tons | -0.30 % |
