Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 2221 | Thousand metric tons | NA |
| 2004 | 2386 | Thousand metric tons | 7.43% |
| 2005 | 2289 | Thousand metric tons | -4.07% |
| 2006 | 2185 | Thousand metric tons | -4.54% |
| 2007 | 2134 | Thousand metric tons | -2.33% |
| 2008 | 2069 | Thousand metric tons | -3.05% |
| 2009 | 1601 | Thousand metric tons | -22.62% |
| 2010 | 1913 | Thousand metric tons | 19.49% |
| 2011 | 1959 | Thousand metric tons | 2.40% |
| 2012 | 1955 | Thousand metric tons | -0.20% |
| 2013 | 1802 | Thousand metric tons | -7.83% |
