Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 240000 | Metric tons | NA |
| 2004 | 240000 | Metric tons | 0.00% |
| 2005 | 240000 | Metric tons | 0.00% |
| 2006 | 240000 | Metric tons | 0.00% |
| 2007 | 230000 | Metric tons | -4.17% |
| 2008 | 230000 | Metric tons | 0.00% |
| 2009 | 220000 | Metric tons | -4.35% |
| 2010 | 210000 | Metric tons | -4.55% |
| 2011 | 200000 | Metric tons | -4.76% |
| 2012 | 200000 | Metric tons | 0.00% |
| 2013 | 190000 | Metric tons | -5.00% |
