US directors’ and officers’ (D&O) insurance rates fell by an average of 4.8% in the first quarter, according to Aon.

“The overall increase in capacity, coupled with some potential new players in the primary D&O space, should make for a stable but improving… marketplace [this year],” the broker’s quarterly overview says.

Surplus capacity and generally positive property and casualty underwriting results will continue to create a stable D&O pricing environment for public companies.

The number of US federal securities class actions was “essentially flat”, with 33 filings in the first quarter, compared with 34 in the corresponding period last year.

However, the report notes that all types of litigation in the D&O area have risen since the global financial crisis – including credit crisis filings, merger objection cases and suits brought by law enforcement agencies and regulators, breaches of fiduciary duty and derivative actions.

A relatively small group of primary carriers are bearing the brunt of this increase.