Warren Buffett’s Berkshire Hathaway Inc. BRK.B -2.50% swung to a first-quarter loss as the selloff in markets hit the company’s vast investments, though the company’s operating earnings rose in the quarter.

Berkshire’s earnings are especially volatile due to an accounting rule that went into effect in 2018 requiring companies to include unrealised investment gains or losses in their net income. Berkshire holds large stock investments, and their quarterly changes in value can have a big effect on Berkshire’s net income.