Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 12.8249998092651 | Thousand metric tons | NA |
| 2004 | 11.1719999313354 | Thousand metric tons | -12.89% |
| 2005 | 14.2609996795654 | Thousand metric tons | 27.65% |
| 2006 | 9.56700038909912 | Thousand metric tons | -32.91% |
| 2007 | 14.460000038147 | Thousand metric tons | 51.14% |
| 2008 | 14.8179998397827 | Thousand metric tons | 2.48% |
| 2009 | 6.79199981689453 | Thousand metric tons | -54.16% |
| 2010 | 12.96399974823 | Thousand metric tons | 90.87% |
| 2011 | 13.9650001525879 | Thousand metric tons | 7.72% |
| 2012 | 13.9449996948242 | Thousand metric tons | -0.14% |
| 2013 | 15.8240003585815 | Thousand metric tons | 13.47% |
