US manufacturing activity contracted in May for a third consecutive month, as new orders and production continued to shrink and exports and imports plunged as President Donald Trump's "ever-changing" tariff policies are scrambling trade flows.

The Institute for Supply Management's (ISM) manufacturing purchasing manager's index (PMI) released today fell to 48.5 in May, down from 48.7 in April, suggesting deepening contraction in the factory sector. Readings below 50 signal contraction while those above that threshold mark expansion. The three-month contraction follows two months of slim factory expansion after 26 months of contraction.

The new orders index for manufacturers rose by 0.4 percentage points to 47.6, signaling an easing contraction in activity, the survey showed on Monday. The production index rose by 1.4 points to 45.4, still in contraction territory for a third month.

The new export order index fell by three points to 40.1, while the imports index fell by 7.2 points to 39.9, showing "extreme contraction."

"The rate of decrease for the new export orders index continues to be the fastest since the coronavirus pandemic, and excluding Covid-19, the reading is the lowest since the Great Recession," ISM said.

"Imports continue to contract as demand has reduced the need to maintain import levels from previous months, as well as due to the impact of tariff pricing," the report said.

The inventory index fell by 4.1 points to 46.7, entering contraction and showing the "pull forward of materials by companies to minimize the financial impacts of tariffs is largely completed."

The prices index came in at 69.4 in May, down from 0.4 points, signaling a slowing expansion in prices.

"There is continued softening of demand in the commercial vehicle market, primarily related to higher prices and economic uncertainty," a transportation vehicle executive said in the survey. "The impact of ever-changing trade policies of the current administration has wreaked havoc on suppliers' ability to react and remain profitable."

Despite the weakness in manufacturing, services activity — the largest part of the US economy — is expected to show expansion at 52 for the month, according to economists surveyed by Trading Economics ahead of that ISM report expected on Wednesday.

By Bob Willis