Household spending may be running out of momentum, economists say, as Americans face the highest inflation in four decades and incomes that haven’t kept up with price increases. U.S. consumers are estimated to have boosted their seasonally adjusted spending by 0.4% in May, a slowdown from the 0.9% increase in April , according to economists surveyed by The Wall Street Journal. The Commerce Department will release its May personal-consumption expenditures report on Thursday at 8:30am ET.