US commercial insurance rates are expected to climb across many lines of business in 2012, according to a new report from UK-based insurance broker Marsh.

Marsh said substantial catastrophe losses and reduced investment returns prompted many US insureds to seek rate increases in 2011, most notably in the property market.

The report finds that property insurance rate increases are expected to accelerate in 2012, especially for insureds with significant catastrophe exposures or loss histories, it notes.

According to report, half of US clients surveyed experienced property rate increases in the second half of 2011.

During the fourth quarter of 2011, insureds with large catastrophe exposures and those with significant losses in 2011 typically saw rate increases of 10% or more.

Primary casualty insurance pricing decreases moderated in 2011. With general liability rates ranging between 5% increases and 5% decreases in the fourth quarter; insureds can expect to be flat to up 5% in 2012 depending on exposure.

For excess casualty, lead umbrella rates generally were flat to up 10% in the fourth quarter of 2011, excess layers typically were flat to up 5%, and market capacity is expected to shrink in 2012 for certain risks.