Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3217 | Thousand metric tons | NA |
| 2003 | 3465 | Thousand metric tons | 7.71 % |
| 2004 | 3828.67700195313 | Thousand metric tons | 10.50 % |
| 2005 | 3978.05590820313 | Thousand metric tons | 3.90 % |
| 2006 | 4238.81787109375 | Thousand metric tons | 6.56 % |
| 2007 | 4898.52978515625 | Thousand metric tons | 15.56 % |
| 2008 | 4804.84521484375 | Thousand metric tons | -1.91 % |
