Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 40745 | Metric tons | NA |
| 2004 | 44207 | Metric tons | 8.50% |
| 2005 | 42087 | Metric tons | -4.80% |
| 2006 | 45169 | Metric tons | 7.32% |
| 2007 | 44000 | Metric tons | -2.59% |
| 2008 | 56500 | Metric tons | 28.41% |
| 2009 | 56333 | Metric tons | -0.30% |
| 2010 | 49038 | Metric tons | -12.95% |
| 2011 | 50000 | Metric tons | 1.96% |
| 2012 | 52000 | Metric tons | 4.00% |
