Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 419.371002197266 | Thousand metric tons | NA |
| 2003 | 429.170013427734 | Thousand metric tons | 2.34 % |
| 2004 | 412.238006591797 | Thousand metric tons | -3.95 % |
| 2005 | 362.105987548828 | Thousand metric tons | -12.16 % |
| 2006 | 411.972991943359 | Thousand metric tons | 13.77 % |
| 2007 | 421.710998535156 | Thousand metric tons | 2.36 % |
| 2008 | 455.100006103516 | Thousand metric tons | 7.92 % |
| 2009 | 350 | Thousand metric tons | -23.09 % |
