Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1955 | Thousand metric tons | NA |
| 2004 | 1950 | Thousand metric tons | -0.26% |
| 2005 | 1749 | Thousand metric tons | -10.31% |
| 2006 | 1936 | Thousand metric tons | 10.69% |
| 2007 | 2143 | Thousand metric tons | 10.69% |
| 2008 | 1951.59997558594 | Thousand metric tons | -8.93% |
| 2009 | 1704 | Thousand metric tons | -12.69% |
| 2010 | 1799 | Thousand metric tons | 5.58% |
| 2011 | 2036.30004882813 | Thousand metric tons | 13.19% |
| 2012 | 1779 | Thousand metric tons | -12.64% |
| 2013 | 1665 | Thousand metric tons | -6.41% |
