Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2005 | 1352 | Thousand metric tons | NA |
| 2006 | 1409 | Thousand metric tons | 4.22% |
| 2007 | 1443 | Thousand metric tons | 2.41% |
| 2008 | 1500 | Thousand metric tons | 3.95% |
| 2009 | 949.986022949219 | Thousand metric tons | -36.67% |
| 2010 | 1309 | Thousand metric tons | 37.79% |
| 2011 | 1494.84997558594 | Thousand metric tons | 14.20% |
| 2012 | 1425 | Thousand metric tons | -4.67% |
| 2013 | 1400 | Thousand metric tons | -1.75% |
