Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 241 | Thousand metric tons | NA |
| 2003 | 236 | Thousand metric tons | -2.07% |
| 2004 | 241.871994018555 | Thousand metric tons | 2.49% |
| 2005 | 266.027008056641 | Thousand metric tons | 9.99% |
| 2006 | 240 | Thousand metric tons | -9.78% |
| 2007 | 200 | Thousand metric tons | -16.67% |
| 2008 | 240 | Thousand metric tons | 20.00% |
| 2009 | 220 | Thousand metric tons | -8.33% |
| 2010 | 270 | Thousand metric tons | 22.73% |
| 2011 | 290 | Thousand metric tons | 7.41% |
| 2012 | 300 | Thousand metric tons | 3.45% |
