Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 48368 | Thousand metric tons | NA |
| 2004 | 50426.69921875 | Thousand metric tons | 4.26% |
| 2005 | 49175 | Thousand metric tons | -2.48% |
| 2006 | 51683 | Thousand metric tons | 5.10% |
| 2007 | 51523 | Thousand metric tons | -0.31% |
| 2008 | 48300 | Thousand metric tons | -6.26% |
| 2009 | 43930 | Thousand metric tons | -9.05% |
| 2010 | 48200 | Thousand metric tons | 9.72% |
| 2011 | 48000 | Thousand metric tons | -0.41% |
| 2012 | 49000 | Thousand metric tons | 2.08% |
