Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 634 | Thousand metric tons | NA |
| 2004 | 696 | Thousand metric tons | 9.78% |
| 2005 | 685 | Thousand metric tons | -1.58% |
| 2006 | 551 | Thousand metric tons | -19.56% |
| 2007 | 635 | Thousand metric tons | 15.25% |
| 2008 | 615 | Thousand metric tons | -3.15% |
| 2009 | 609.276000976563 | Thousand metric tons | -0.93% |
| 2010 | 627.93798828125 | Thousand metric tons | 3.06% |
| 2011 | 567.504028320313 | Thousand metric tons | -9.62% |
| 2012 | 487.553009033203 | Thousand metric tons | -14.09% |
| 2013 | 464.8330078125 | Thousand metric tons | -4.66% |
