Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1340 | Thousand metric tons | NA |
| 2003 | 1400 | Thousand metric tons | 4.48% |
| 2004 | 1400 | Thousand metric tons | 0.00% |
| 2005 | 1500 | Thousand metric tons | 7.14% |
| 2006 | 1568 | Thousand metric tons | 4.53% |
| 2007 | 2500 | Thousand metric tons | 59.44% |
| 2008 | 3800 | Thousand metric tons | 52.00% |
| 2009 | 4095 | Thousand metric tons | 7.76% |
| 2010 | 5280 | Thousand metric tons | 28.94% |
| 2011 | 5000 | Thousand metric tons | -5.30% |
| 2012 | 5500 | Thousand metric tons | 10.00% |
