August 18th, 2009, 1:44 pm
Particularly right now, there is a large negative CDS-bond basis in the market, which means CDS spreads are typically lower than Z-spreads, asset swap spreads or option-adjusted spreads, in some cases by > 100bp. There are many factors which contribute to this, liquidity premia arguably being foremost. So pricing a CDS spread using bond spreads is likely to give you an overly cheap credit estimate. This is where quasi-science becomes quasi-art, but you might adjust for the average CDS-cash basis in the company's sector or subsector.