Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 38.8559989929199 | Thousand metric tons | NA |
| 2004 | 32.1479988098145 | Thousand metric tons | -17.26% |
| 2005 | 37.7900009155273 | Thousand metric tons | 17.55% |
| 2006 | 36.2080001831055 | Thousand metric tons | -4.19% |
| 2007 | 36.2000007629395 | Thousand metric tons | -0.02% |
| 2008 | 36.2000007629395 | Thousand metric tons | 0.00% |
| 2009 | 6.19000005722046 | Thousand metric tons | -82.90% |
| 2010 | 5.56799983978271 | Thousand metric tons | -10.05% |
| 2011 | 27.0610008239746 | Thousand metric tons | 386.01% |
| 2012 | 30 | Thousand metric tons | 10.86% |
| 2013 | 30 | Thousand metric tons | 0.00% |
