Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6800 | Thousand metric tons | NA |
| 2004 | 6800 | Thousand metric tons | 0.00% |
| 2005 | 1609.72094726563 | Thousand metric tons | -76.33% |
| 2006 | 2007.70300292969 | Thousand metric tons | 24.72% |
| 2007 | 1890.02905273438 | Thousand metric tons | -5.86% |
| 2008 | 2150.22094726563 | Thousand metric tons | 13.77% |
| 2009 | 1200.1689453125 | Thousand metric tons | -44.18% |
| 2010 | 939.293029785156 | Thousand metric tons | -21.74% |
| 2011 | 898.200012207031 | Thousand metric tons | -4.37% |
| 2012 | 820 | Thousand metric tons | -8.71% |
| 2013 | 808 | Thousand metric tons | -1.46% |
