Soft market conditions and a near halving in investment returns has seen US-based global broker Aon post a flat first-quarter revenue figure of $US1.9 billion ($2.05 billion).

Total revenue grew 3% from the corresponding quarter last year, and operating income rose only slightly from $US316 million ($331.4 million) in the first quarter of last year to $US326 million ($352.2 million).

Aon’s first quarter was hampered by a $US12 million ($12.96 million) shortfall in investment returns, and a $US33 million ($35.6 million) increase in restructuring expenses from the prior year quarter.

Those losses were offset slightly by improved currency fluctuations and the addition of Allied North America to its balance sheet.

CEO Greg Case says the company’s first quarter was “solid” despite prevailing market conditions.

“Our restructuring programs are expected to deliver additional cost savings and margin improvement, while substantial investments across our organisation… continue to strengthen our client-serving capability,” Mr Case said.