Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 16906 | Thousand metric tons | NA |
| 2003 | 18287 | Thousand metric tons | 8.17 % |
| 2004 | 18205 | Thousand metric tons | -0.45 % |
| 2005 | 19000 | Thousand metric tons | 4.37 % |
| 2006 | 26243.837890625 | Thousand metric tons | 38.13 % |
| 2007 | 31537.544921875 | Thousand metric tons | 20.17 % |
| 2008 | 32000 | Thousand metric tons | 1.47 % |
| 2009 | 33000 | Thousand metric tons | 3.13 % |
