A single rate increase of 3.1% secured by a subsidiary of The Progressive Corp. may be the most impactful of any commercial auto rate hike approved in April, as it stands to boost the group's written premiums by $7.4 million.

Berkshire Hathaway Inc. and The Travelers Companies Inc. also received approvals for significant rate increases during the month.

Berkshire could see the largest cumulative written premium increase of any insurance group, $15.8 million, from six rate hikes. Three increase requests approved for the group, one in New York and two in Ohio, account for nearly 87% of the calculated increase.

Travelers could see the second-largest aggregate positive premium impact at nearly $10.9 million, thanks to 12 hike approvals across six states. About 94.5%, or $10.3 million, of the expected premium increase looks to come from Georgia.

On the other side of the spectrum, Hastings Mutual Insurance Co. obtained approval to cut rates by 1.3%, which could result in the largest premium reduction among the commercial auto insurers. The rate cut will affect more than 4,400 policyholders in Michigan and is set to go into effect on July 1 for both renewal and new business.