Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1600 | Thousand metric tons | NA |
| 2003 | 1800 | Thousand metric tons | 12.50% |
| 2004 | 2077 | Thousand metric tons | 15.39% |
| 2005 | 2200 | Thousand metric tons | 5.92% |
| 2006 | 2200 | Thousand metric tons | 0.00% |
| 2007 | 2300 | Thousand metric tons | 4.55% |
| 2008 | 2300 | Thousand metric tons | 0.00% |
| 2009 | 2900 | Thousand metric tons | 26.09% |
| 2010 | 2900 | Thousand metric tons | 0.00% |
| 2011 | 4960 | Thousand metric tons | 71.03% |
| 2012 | 5000 | Thousand metric tons | 0.81% |
| 2013 | 5100 | Thousand metric tons | 2.00% |
