Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 19363 | Thousand metric tons | NA |
| 2003 | 18474 | Thousand metric tons | -4.59% |
| 2004 | 19050 | Thousand metric tons | 3.12% |
| 2005 | 19891 | Thousand metric tons | 4.41% |
| 2006 | 19294 | Thousand metric tons | -3.00% |
| 2007 | 18957 | Thousand metric tons | -1.75% |
| 2008 | 17330 | Thousand metric tons | -8.58% |
| 2009 | 15918 | Thousand metric tons | -8.15% |
| 2010 | 16301 | Thousand metric tons | 2.41% |
| 2011 | 16852 | Thousand metric tons | 3.38% |
| 2012 | 15806 | Thousand metric tons | -6.21% |
