Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 460000 | Metric tons | NA |
| 2004 | 492000 | Metric tons | 6.96% |
| 2005 | 542000 | Metric tons | 10.16% |
| 2006 | 550000 | Metric tons | 1.48% |
| 2007 | 550000 | Metric tons | 0.00% |
| 2008 | 550000 | Metric tons | 0.00% |
| 2009 | 375302 | Metric tons | -31.76% |
| 2010 | 419345 | Metric tons | 11.74% |
| 2011 | 429494 | Metric tons | 2.42% |
| 2012 | 440000 | Metric tons | 2.45% |
| 2013 | 440000 | Metric tons | 0.00% |
