Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4699.73876953125 | Thousand metric tons | NA |
| 2004 | 4705.33984375 | Thousand metric tons | 0.12% |
| 2005 | 4548.615234375 | Thousand metric tons | -3.33% |
| 2006 | 4593.076171875 | Thousand metric tons | 0.98% |
| 2007 | 4314 | Thousand metric tons | -6.08% |
| 2008 | 3664 | Thousand metric tons | -15.07% |
| 2009 | 2856 | Thousand metric tons | -22.05% |
| 2010 | 3078 | Thousand metric tons | 7.77% |
| 2011 | 3003 | Thousand metric tons | -2.44% |
| 2012 | 2877 | Thousand metric tons | -4.20% |
| 2013 | 3000 | Thousand metric tons | 4.28% |
