Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 11089 | Thousand metric tons | NA |
| 2003 | 11215 | Thousand metric tons | 1.14% |
| 2004 | 11405 | Thousand metric tons | 1.69% |
| 2005 | 11216 | Thousand metric tons | -1.66% |
| 2006 | 12119 | Thousand metric tons | 8.05% |
| 2007 | 11900 | Thousand metric tons | -1.81% |
| 2008 | 10071 | Thousand metric tons | -15.37% |
| 2009 | 7623 | Thousand metric tons | -24.31% |
| 2010 | 7882 | Thousand metric tons | 3.40% |
| 2011 | 8529 | Thousand metric tons | 8.21% |
| 2012 | 8500 | Thousand metric tons | -0.34% |
