Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3085 | Thousand metric tons | NA |
| 2003 | 2450 | Thousand metric tons | -20.58% |
| 2004 | 2380 | Thousand metric tons | -2.86% |
| 2005 | 2496 | Thousand metric tons | 4.87% |
| 2006 | 2790 | Thousand metric tons | 11.78% |
| 2007 | 2700 | Thousand metric tons | -3.23% |
| 2008 | 3097 | Thousand metric tons | 14.70% |
| 2009 | 2342 | Thousand metric tons | -24.38% |
| 2010 | 2138 | Thousand metric tons | -8.71% |
| 2011 | 2318 | Thousand metric tons | 8.42% |
| 2012 | 2500 | Thousand metric tons | 7.85% |
