For example, TBA mortgage securities often trade with interest rates in increments of 0.5%. Therefore, assuming par value is 100, if Fannie Mae 8% mortgage securities are trading at 99.5 and Fannie Mae 8.5% mortgage securities are trading at 100.75, Fannie Mae's 8% security would be the current coupon.
A principle of mortgage analysis is that the higher a mortgage-backed security's coupon is relative to the current coupon, the more likely that mortgage-backed security is to prepay. Mortgage investors make this relative value analysis in calculating mortgage-backed security yields and valuations.
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діюча відсоткова (процентна) ставка; ринкова відсоткова (процентна) ставка