Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 835 | Thousand metric tons | NA |
| 2004 | 846 | Thousand metric tons | 1.32% |
| 2005 | 869 | Thousand metric tons | 2.72% |
| 2006 | 891 | Thousand metric tons | 2.53% |
| 2007 | 947 | Thousand metric tons | 6.29% |
| 2008 | 950 | Thousand metric tons | 0.32% |
| 2009 | 1079 | Thousand metric tons | 13.58% |
| 2010 | 1623.19201660156 | Thousand metric tons | 50.43% |
| 2011 | 1749.06799316406 | Thousand metric tons | 7.75% |
| 2012 | 1853 | Thousand metric tons | 5.94% |
| 2013 | 1900 | Thousand metric tons | 2.54% |
