Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1700 | Thousand metric tons | NA |
| 2003 | 2100 | Thousand metric tons | 23.53% |
| 2004 | 2621 | Thousand metric tons | 24.81% |
| 2005 | 2686 | Thousand metric tons | 2.48% |
| 2006 | 3611 | Thousand metric tons | 34.44% |
| 2007 | 3880 | Thousand metric tons | 7.45% |
| 2008 | 3991 | Thousand metric tons | 2.86% |
| 2009 | 4000 | Thousand metric tons | 0.23% |
| 2010 | 4500 | Thousand metric tons | 12.50% |
| 2011 | 5000 | Thousand metric tons | 11.11% |
| 2012 | 5200 | Thousand metric tons | 4.00% |
