Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 191.399993896484 | Thousand metric tons | NA |
| 2004 | 195.399993896484 | Thousand metric tons | 2.09% |
| 2005 | 192.899993896484 | Thousand metric tons | -1.28% |
| 2006 | 194.199996948242 | Thousand metric tons | 0.67% |
| 2007 | 182.569000244141 | Thousand metric tons | -5.99% |
| 2008 | 180 | Thousand metric tons | -1.41% |
| 2009 | 170.64599609375 | Thousand metric tons | -5.20% |
| 2010 | 168 | Thousand metric tons | -1.55% |
| 2011 | 141 | Thousand metric tons | -16.07% |
| 2012 | 110 | Thousand metric tons | -21.99% |
