Swap spreads conventions

Figure 8.2 shows the Bloomberg YAS page for Tesco bond SVi% 2019, as at October 9, 2014. The bond has a price of 109.345 and yield to maturity of 3.46%. On the date, the yield spread over a government bond benchmark UK 41 % Treasury 2019 is 200 basis points. The G-spread over an interpolated government bond is 181.5 basis points. Conventionally, the difference between these two spreads is narrow. We see also that the asset-swap spread is 173.6 basis points and Z-spread is 166.3 basis points. 

Chapter 8 shows several spread measures that can be used to compare fixed-rate bonds. Conventionally for floating-rate notes, traders use the discounted margin. To analyse a floating-rate note with a fixed-rate note, one method is to compare the discounted margin of a floater with the asset swap spread of fixed-rate bonds. 

Given the swap rate, the swap spread can be determined. For example, since this is a 3-year swap, the convention is to use the 3-year rate on the euro benchmark yield curve. If the yield on that issue is 4.5875%, the swap spread is 40 basis points (4.9875% - 4.5875%). 

Put simply, the Z-spread is the basis point spread that would need to be added to the implied spot yield curve such that the discounted cash flows of the bond are equal to its present value (its current market price). Each bond cash flow is discounted by the relevant spot rate for its maturity term. How does this differ from the conventional asset-swap spread Essentially, in its use of zero-coupon rates when assigning a value to a bond. Each cash flow is discounted using its own particular zero-coupon rate. The bond s price at any time can be taken to be the market s value... 

In practice, the Z-spread, especially for shorter-dated bonds and for better credit-quality bonds, does not differ greatly from the conventional asset-swap spread. The Z-spread is usually the higher spread of the two, following the logic of spot rates, but not always. If it differs greatly, then the bond can be considered to be mispriced. 

Craisider a hypothetical situation. Assume that an option-free bond paying a semi-annual coupon 5.5% on par value, with a maturity of 5 years and discount rate of 8.04% (EUR 5-year swap rate of 1.04% plus credit spread of 700 basis points). Therefore, the valuation of a conventional bond is performed as follows (Figure 9.4). 

In the pre-euro days, traders were usually organized by currency. Now, sector specialization is the rule. For most issues, buy or sell indications are initially indicated on a spread basis. The spread can be either over the swap curve or over a specified government benchmark. A corporate bond issue keeps the same benchmark for its entire life they roll down the curve together. This is in contrast to the United States, where the convention is to quote a corporate bond s spread over the nearest on-the-run (most recently issued) 2-, 5-, 10-, or 30-year maturity Treasury bond. 

As discussed above, vanilla swap rates are often quoted as a spread that is a function mainly of the credit spread required by the market over the risk-free government rate. This convention is logical, because government bonds are the principal instrument banks use to hedge their swap books. It is unwieldy, however, when applied to nonstandard tailor-made swaps, each of which has particular characteristics that call for particular spread calculations. As a result, banks use zero-coupon pricing, a standard method that can be applied to all swaps. 

The conventional approach for analyzing an asset swap uses the bonds yield-to-maturity (YTM) in calculating the spread. The assumptions implicit in the YTM calculation (see Chapter 2) make this spread problematic for relative analysis, so market practitioners use what is termed the Z-spread instead. The Z-spread uses the zero-coupon yield curve to calculate spread, so is a more realistic, and effective, spread to use. The zero-coupon curve used in the calculation is derived from the interest-rate swap curve. 

---