Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 502800 | Metric tons | NA |
| 2003 | 495000 | Metric tons | -1.55% |
| 2004 | 531000 | Metric tons | 7.27% |
| 2005 | 512000 | Metric tons | -3.58% |
| 2006 | 497000 | Metric tons | -2.93% |
| 2007 | 452000 | Metric tons | -9.05% |
| 2008 | 429400 | Metric tons | -5.00% |
| 2009 | 439000 | Metric tons | 2.24% |
| 2010 | 425400 | Metric tons | -3.10% |
| 2011 | 426700 | Metric tons | 0.31% |
| 2012 | 427100 | Metric tons | 0.09% |
