The term “bond spreads” or “spreads” refers to the interest rate differential between two bonds. Mathematically, a bond spread is the simple subtraction of one bond yield from another. Bond spreads are the common way that market participants compare the value of one bond to another, much like “price-earnings ratios” are used for equities.
Bond spreads reflect the relative risks of the bonds being compared. The higher the spread, the higher the risk usually is. People referring to bond spreads are generally talking about comparing the yields on federal government bonds, generally considered a country’s most creditworthy bonds, to the bonds of other issuers such as provinces, municipalities or corporations. Bond spreads can also be calculated between bonds of different maturity, interest rate coupon or even different countries and currencies.