Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4677 | Thousand metric tons | NA |
| 2004 | 4847 | Thousand metric tons | 3.63% |
| 2005 | 5444 | Thousand metric tons | 12.32% |
| 2006 | 5547 | Thousand metric tons | 1.89% |
| 2007 | 5808 | Thousand metric tons | 4.71% |
| 2008 | 5795.01708984375 | Thousand metric tons | -0.22% |
| 2009 | 4353.2578125 | Thousand metric tons | -24.88% |
| 2010 | 5621.19091796875 | Thousand metric tons | 29.13% |
| 2011 | 5815.47021484375 | Thousand metric tons | 3.46% |
| 2012 | 5751.35693359375 | Thousand metric tons | -1.10% |
