Warren Buffett’s Berkshire Hathaway Swings to a Rare Loss on Unrealized Investment Hit

Revenue for the conglomerate falls to $58.47 billion due to a drop in insurance premiums earned

Warren Buffett’s Berkshire Hathaway Inc. swung to a rare loss in the first quarter, hurt by lower insurance premiums and the impact of an accounting rule change on unrealized investment losses.

Berkshire’s results were released Saturday morning ahead of the company’s widely attended annual meeting in Omaha, Neb.

Berkshire reported a first-quarter...