Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 421 | Thousand metric tons | NA |
| 2003 | 394 | Thousand metric tons | -6.41% |
| 2004 | 490.372009277344 | Thousand metric tons | 24.46% |
| 2005 | 501.585998535156 | Thousand metric tons | 2.29% |
| 2006 | 615.072021484375 | Thousand metric tons | 22.63% |
| 2007 | 706.703979492188 | Thousand metric tons | 14.90% |
| 2008 | 705 | Thousand metric tons | -0.24% |
| 2009 | 600 | Thousand metric tons | -14.89% |
| 2010 | 637 | Thousand metric tons | 6.17% |
| 2011 | 834 | Thousand metric tons | 30.93% |
| 2012 | 765.299987792969 | Thousand metric tons | -8.24% |
| 2013 | 676.200012207031 | Thousand metric tons | -11.64% |
