The CDS spread pricing model uses “Risk free rate” to discount the PV and the Z-spread also uses “Risk free rate” to compute the spread. But the given example uses repo rate that comparing to Libor:
For “Negative Basis Trade”
- Z spread = 100 bps
- CDS spread = 40 bps
- Repo rate = 2% or Libor plus 20 bps
Thus, long the bond to receive at 100bps and borrow from repo at 2% or Libor plus 20 bps and buy CDS protection at 40 bps.
$$100 - (40+20) = 40bps$$
Q: Why does this example use the spread over Libor instead of the spread over “Risk free rate” (SOFR, Secured Overnight Financing Rate) in order to be consistent?