Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 425945 | Metric tons | NA |
| 2004 | 455282 | Metric tons | 6.89% |
| 2005 | 421629 | Metric tons | -7.39% |
| 2006 | 425000 | Metric tons | 0.80% |
| 2007 | 430000 | Metric tons | 1.18% |
| 2008 | 435000 | Metric tons | 1.16% |
| 2009 | 432000 | Metric tons | -0.69% |
| 2010 | 430000 | Metric tons | -0.46% |
| 2011 | 425000 | Metric tons | -1.16% |
| 2012 | 420000 | Metric tons | -1.18% |
| 2013 | 400000 | Metric tons | -4.76% |
