This excerpt taken from the WMT 8-K filed Mar 7, 2006.
Interest Rate means the annual rate at which interest is deemed to accrue on the amounts credited in a Deferral Account for a Director. The annual rate shall be set by the Board or a committee of the Board and may be changed from time to time as necessary to reflect prevailing interest rates. [NOTE: The annual rate in effect for a Plan Year for this purpose shall be determined in accordance with the following formula in effect as of October 3, 2004: the mid-term rate on 10-year Treasury notes determined as of the first Business Day of January of each Plan Year, plus 270 basis points. Such formula shall not be modified on or after October 3, 2004. Notwithstanding the preceding, in light of uncertainty regarding whether adjustment of the annual rate would constitute a material modification of the Plan for Code Section 409A purposes, the annual rate was not adjusted for 2005. The annual rate for 2006 and future years will be adjusted in accordance with the above formula.]