Purchasing managers sit at the intersection of supply and demand. They see orders coming in before revenue is booked, they track supplier delivery times before supply chain data is published, and they make hiring decisions before employment data is collected. The ISM PMI captures their collective assessment through a monthly survey, and the result has been one of the most reliable economic indicators for decades.
The index is structured as a diffusion index around 50. Readings above 50 indicate expansion, below 50 indicate contraction. But the level alone is not the whole story. The direction and rate of change matter significantly. A reading of 52 that was 56 three months ago tells a different story than a reading of 52 that was 48 three months ago.
Historically, ISM Manufacturing PMI readings below 43 have been consistent with recessions. The services PMI matters too, arguably more in the modern economy where services dominate GDP. When both manufacturing and services PMIs are declining simultaneously, the probability of a broad economic slowdown increases substantially.
For equity markets, the PMI-to-returns relationship is not perfectly linear but it is directional. Periods when the PMI is above 50 and rising have historically coincided with the strongest equity returns. When the PMI is below 50 and falling, equity returns have been weakest. The intermediate states produce middling results on average.
The sub-components carry useful information beyond the headline number. New orders minus inventories provides a signal about future production demand. When new orders are strong but inventories are low, production needs to ramp up, which is bullish. When new orders are weak but inventories are high, production will need to slow, which pressures earnings.
The employment sub-component tends to lead the official BLS employment data by a month or more. If ISM employment is declining, the next few payroll reports are more likely to disappoint. This gives you a head start on one of the most market-moving data releases.
The prices paid sub-component has predictive value for PPI and CPI readings. When ISM prices paid spikes, inflation pressures are building in the pipeline. When it drops, those pressures are easing. The lead time is typically one to three months.
One practical approach is to track the PMI in conjunction with market positioning. When the PMI is declining and approaching 50 from above, but equity markets are still near highs, there is a disconnect that tends to resolve in the direction the data is pointing. These divergences between economic reality and market pricing are where actionable opportunities often emerge.