Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 10256 | Thousand metric tons | NA |
| 2004 | 11088 | Thousand metric tons | 8.11% |
| 2005 | 12444 | Thousand metric tons | 12.23% |
| 2006 | 11424 | Thousand metric tons | -8.20% |
| 2007 | 10855 | Thousand metric tons | -4.98% |
| 2008 | 11160 | Thousand metric tons | 2.81% |
| 2009 | 11560 | Thousand metric tons | 3.58% |
| 2010 | 12055 | Thousand metric tons | 4.28% |
| 2011 | 11404 | Thousand metric tons | -5.40% |
| 2012 | 10822 | Thousand metric tons | -5.10% |
| 2013 | 11000 | Thousand metric tons | 1.64% |
