Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1380.59997558594 | Thousand metric tons | NA |
| 2004 | 1457.40002441406 | Thousand metric tons | 5.56% |
| 2005 | 1498.5 | Thousand metric tons | 2.82% |
| 2006 | 1605 | Thousand metric tons | 7.11% |
| 2007 | 1655 | Thousand metric tons | 3.12% |
| 2008 | 1661.09997558594 | Thousand metric tons | 0.37% |
| 2009 | 1536 | Thousand metric tons | -7.53% |
| 2010 | 1536 | Thousand metric tons | 0.00% |
| 2011 | 1440 | Thousand metric tons | -6.25% |
| 2012 | 1436 | Thousand metric tons | -0.28% |
| 2013 | 1304.30004882813 | Thousand metric tons | -9.17% |
