Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 378.587005615234 | Thousand metric tons | NA |
| 2003 | 245.408996582031 | Thousand metric tons | -35.18% |
| 2004 | 89.6640014648438 | Thousand metric tons | -63.46% |
| 2005 | 32.2029991149902 | Thousand metric tons | -64.08% |
| 2006 | 87.9700012207031 | Thousand metric tons | 173.17% |
| 2007 | 61.0769996643066 | Thousand metric tons | -30.57% |
| 2008 | 65 | Thousand metric tons | 6.42% |
| 2009 | 44.5519981384277 | Thousand metric tons | -31.46% |
| 2010 | 45.6100006103516 | Thousand metric tons | 2.37% |
| 2011 | 46 | Thousand metric tons | 0.86% |
| 2012 | 48 | Thousand metric tons | 4.35% |
