The ease with which investors can transact deals in the credit derivatives market has improved on average over time and has apparently been best during some of the periods of greatest stress, according to new research.

A new measure of liquidity in single-name credit default swaps, which provide a kind of insurance against non-payment of debt by individual companies, shows that liquidity in the market peaked around the time of the collapse of Lehman Brothers, according to Fitch Solutions, a valuation and asset services arm of Fitch Ratings.