Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 4584 | Thousand metric tons | NA |
| 2003 | 4632 | Thousand metric tons | 1.05% |
| 2004 | 4494 | Thousand metric tons | -2.98% |
| 2005 | 5092.8388671875 | Thousand metric tons | 13.33% |
| 2006 | 5088.8798828125 | Thousand metric tons | -0.08% |
| 2007 | 5000 | Thousand metric tons | -1.75% |
| 2008 | 4819 | Thousand metric tons | -3.62% |
| 2009 | 4759 | Thousand metric tons | -1.25% |
| 2010 | 5139 | Thousand metric tons | 7.98% |
| 2011 | 5480 | Thousand metric tons | 6.64% |
| 2012 | 5500 | Thousand metric tons | 0.36% |
