Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 109.544998168945 | Thousand metric tons | NA |
| 2004 | 68.0309982299805 | Thousand metric tons | -37.90% |
| 2005 | 62.6040000915527 | Thousand metric tons | -7.98% |
| 2006 | 50.7270011901855 | Thousand metric tons | -18.97% |
| 2007 | 64.4990005493164 | Thousand metric tons | 27.15% |
| 2008 | 55.7099990844727 | Thousand metric tons | -13.63% |
| 2009 | 85.5299987792969 | Thousand metric tons | 53.53% |
| 2010 | 97.3030014038086 | Thousand metric tons | 13.76% |
| 2011 | 135.067993164063 | Thousand metric tons | 38.81% |
| 2012 | 128 | Thousand metric tons | -5.23% |
| 2013 | 150 | Thousand metric tons | 17.19% |
