Administration, or the Rural Housing Service can be included in a mortgage pool guaranteed by Gin- nie Mae. The maximum loan size is set by Congress, based on the maxi- mum amount that the FHA, VA, or RHS may guarantee. The maximum for a given loan varies with the region of the country and type of resi- dential property. The passthroughs issued by the Federal National Mortgage Associa- tion (nicknamed "Fannie Mae") are called mortgage-backed securities (MBSs). Although a guarantee of Fannie Mae is not a guarantee by the U.S. government, most market participants view Fannie Mae MBSs as similar, although not identical, in credit worthiness to Ginnie Mae passthroughs. All Fannie Mae MBSs carry its guarantee of timely pay- ment of both interest and principal. The Federal Home Loan Mortgage Corporation (nicknamed "Freddie Mac") is a government sponsored enterprise that issues a passthrough security that is called a participation certificate (PC). As with Fannie Mae MBS, a guarantee of Freddie Mac is not a guarantee by the U.S. govern- ment, but most market participants view Freddie Mac PCs as similar, although not identical, in credit worthiness to Ginnie Mae passthroughs. Freddie Mac has issued PCs with different types of guarantee. The old PCs issued by Freddie Mac guarantee the timely payment of interest; the scheduled principal is passed through as it is collected, with Freddie Mac only guaranteeing that the scheduled payment will be made no later than one year after it is due. Today, Freddie Mac issues PCs under its "Gold Program" in which both the timely payment of interest and principal are guaranteed.   Price Quotes and Trading Procedures Passthroughs are quoted in the same manner as U.S. Treasury coupon securities. A quote of 94-05 means 94 and ⁵ ₃₂nds of par value, or 94.15625% of par value. The price that the buyer pays the seller is the agreed upon sale price plus accrued interest. Given the par value, the dollar price (excluding accrued interest) is affected by the amount of the mortgage pool balance outstanding. The pool factor indicates the per- centage of the initial mortgage balance still outstanding. So, a pool fac- tor of 90 means that 90% of the original mortgage pool balance is outstanding. The pool factor is reported by the agency each month.     The dollar price paid for just the principal is found as follows given the agreed upon price, par value, and the months pool factor provided by the agency:   Price = Par value ´ Pool factor