Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 430 | Thousand metric tons | NA |
| 2003 | 540 | Thousand metric tons | 25.58% |
| 2004 | 650 | Thousand metric tons | 20.37% |
| 2005 | 1009.40002441406 | Thousand metric tons | 55.29% |
| 2006 | 1020 | Thousand metric tons | 1.05% |
| 2007 | 1060 | Thousand metric tons | 3.92% |
| 2008 | 2587.92456054688 | Thousand metric tons | 144.14% |
| 2009 | 3593.39624023438 | Thousand metric tons | 38.85% |
| 2010 | 3720.943359375 | Thousand metric tons | 3.55% |
| 2011 | 4168.3017578125 | Thousand metric tons | 12.02% |
| 2012 | 4170 | Thousand metric tons | 0.04% |
