Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 14336 | Thousand metric tons | NA |
| 2003 | 17243 | Thousand metric tons | 20.28% |
| 2004 | 15690 | Thousand metric tons | -9.01% |
| 2005 | 17860 | Thousand metric tons | 13.83% |
| 2006 | 18400 | Thousand metric tons | 3.02% |
| 2007 | 19480 | Thousand metric tons | 5.87% |
| 2008 | 19629 | Thousand metric tons | 0.76% |
| 2009 | 19457 | Thousand metric tons | -0.88% |
| 2010 | 19762 | Thousand metric tons | 1.57% |
| 2011 | 21198 | Thousand metric tons | 7.27% |
| 2012 | 21726 | Thousand metric tons | 2.49% |
