Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1631 | Thousand metric tons | NA |
| 2003 | 1650 | Thousand metric tons | 1.16% |
| 2004 | 1420 | Thousand metric tons | -13.94% |
| 2005 | 1613 | Thousand metric tons | 13.59% |
| 2006 | 1695 | Thousand metric tons | 5.08% |
| 2007 | 1700 | Thousand metric tons | 0.29% |
| 2008 | 1747 | Thousand metric tons | 2.76% |
| 2009 | 1093 | Thousand metric tons | -37.44% |
| 2010 | 1298 | Thousand metric tons | 18.76% |
| 2011 | 1387 | Thousand metric tons | 6.86% |
| 2012 | 1500 | Thousand metric tons | 8.15% |
