Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2618 | Thousand metric tons | NA |
| 2003 | 2237 | Thousand metric tons | -14.55 % |
| 2004 | 2400 | Thousand metric tons | 7.29 % |
| 2005 | 1590 | Thousand metric tons | -33.75 % |
| 2006 | 1600 | Thousand metric tons | 0.63 % |
| 2007 | 2184.72900390625 | Thousand metric tons | 36.55 % |
| 2008 | 1810.60595703125 | Thousand metric tons | -17.12 % |
| 2009 | 1800 | Thousand metric tons | -0.59 % |
