Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 40600 | Thousand metric tons | NA |
| 2004 | 42300 | Thousand metric tons | 4.19% |
| 2005 | 37200 | Thousand metric tons | -12.06% |
| 2006 | 37900 | Thousand metric tons | 1.88% |
| 2007 | 36300 | Thousand metric tons | -4.22% |
| 2008 | 33700 | Thousand metric tons | -7.16% |
| 2009 | 19000 | Thousand metric tons | -43.62% |
| 2010 | 26800 | Thousand metric tons | 41.05% |
| 2011 | 30200 | Thousand metric tons | 12.69% |
| 2012 | 32100 | Thousand metric tons | 6.29% |
