Corporate liquidity declined marginally in May, according to the Moody’s Investors Service’s liquidity-stress indicator (LSI) published on Thursday.

Moody’s LSI came in at 2.7% in May, up slightly from 2.5% in April. The indicator rises when corporate liquidity appears to weaken, and declines when liquidity improves.

“The LSI has been hovering around historic lows — below 3% — for the past eight months,” says John Puchalla, senior vice president at Moody’s, in a statement. “The consistent strength in the LSI signals healthy liquidity and low default risk for most spec-grade borrowers, with benefits from solid earnings and cash flow on the back of a growing U.S. economy.”

Liquidity downgrades outpaced upgrades by a margin of six to four in May, Moody’s says. A mix of energy, telecom and agricultural products companies accounted for most of the downgrades.

Speculative-grade liquidity downgrades outnumbered upgrades by a margin of 10 to three.

“In some instances, growth-related investments were a contributing factor to the downgrades, and this would be more worrisome if capital market access was weaker, since that might cut off a company’s ability to fund the investments,” says Puchalla.