PMI Definition: The Purchasing Managers’ Index (PMI) is a monthly survey-based indicator that measures whether business activity in manufacturing or services is expanding or contracting. Purchasing managers report whether new orders, output, employment and other measures rose, fell or stayed the same, and the answers are combined into a single number from 0 to 100. A reading above 50 signals expansion compared with the previous month, while a reading below 50 signals contraction.
What Is a PMI?
Every month, thousands of purchasing managers get a short questionnaire. They are the people who buy raw materials, parts and services for their companies, so they see changes in demand before almost anyone else. If orders pick up, they buy more; if orders dry up, they cut back.
That early view is what makes the survey valuable. Official statistics such as GDP arrive weeks or months after the quarter ends and are revised several times. PMI results appear within days of the month closing and describe what companies are doing now rather than what they did a quarter ago.
Two families of PMI dominate. In the United States, the Institute for Supply Management (ISM) has published a manufacturing survey since 1948 and later added services. S&P Global, which absorbed the former Markit surveys, compiles PMIs for more than 40 economies, including the euro area, China, Japan and the UK.
How Is the PMI Calculated?
Each PMI is built from diffusion indices. For every question, the survey counts how many respondents report an increase, a decrease or no change. The index equals the percentage reporting higher plus half the percentage reporting no change.
Now for the mechanics that matter to traders. Suppose 100 manufacturers answer the question on new orders: 40 report more orders, 20 report fewer and 40 report no change. The new orders index is 40 + (0.5 × 40) = 60, which signals clear growth.
Repeat the survey a month later with 25 reporting more, 35 reporting fewer and 40 unchanged. The index drops to 25 + 20 = 45, below the 50 line, even though no company reported a disaster. A PMI measures how widespread a change is, not how large it is.
The headline manufacturing PMI combines several of these sub-indices. ISM weights five equally: new orders, production, employment, supplier deliveries and inventories. Supplier deliveries are inverted, because slower deliveries usually mean suppliers are busy, so longer delivery times push the index up.
Types of PMI
Manufacturing PMI covers factories and is the oldest and most watched version. Factory output swings more than services, so it often turns first at cycle peaks and troughs.
Services PMI covers businesses such as retail, finance, transport and hospitality. In developed economies services make up the larger share of output and jobs, so this survey often says more about overall growth.
Composite PMI blends manufacturing and services output into one number, weighted by each sector’s size. S&P Global also releases flash PMIs about a week before month-end, based on roughly 85% of responses.
PMI vs. GDP
| PMI | GDP | |
|---|---|---|
| What it measures | Breadth of change in business conditions | Total value of goods and services produced |
| Frequency | Monthly | Quarterly in most countries |
| Timing | Days after the month ends, flash before | About a month after the quarter ends |
| Revisions | Rare and small | Several, sometimes large |
| Main weakness | Survey of sentiment, not size of change | Late, backward-looking |
Why Is PMI Important for Traders?
PMI releases move currencies and bond yields because they are the first read on the economy each month. A euro-area composite PMI that beats expectations can lift the euro and push up yields as traders price a firmer central bank. Sub-indices matter too: the prices-paid component often flags cost pressure before CPI data confirm it, and the employment index is read as a preview of non-farm payrolls.
Extreme readings show both the value and the limits of the survey. In April 2020 the ISM manufacturing index fell to 41.5 and the euro-area composite dropped below 14, a record low. Those numbers captured the lockdown shock faster than any official statistic, yet they could not show how deep the fall in output was, because a PMI only counts how many firms got worse.
The biggest limitation is the gap between factories and the wider economy. US manufacturing PMI stayed below 50 from November 2022 until it reached 50.3 in March 2024, while the economy avoided a recession and edged toward a soft landing. Traders who read the manufacturing index alone would have expected a downturn that never came.
Key Takeaways
- A PMI is a monthly survey of purchasing managers that shows whether business activity is expanding (above 50) or contracting (below 50).
- Each index is a diffusion measure: the share of firms reporting improvement plus half the share reporting no change.
- Manufacturing, services and composite PMIs cover different parts of the economy, and services usually carry more weight in developed markets.
- PMIs arrive earlier and are revised less than GDP, which is why they often move currencies and bond yields on release day.
- A PMI measures how widespread a change is, not its size, so a weak manufacturing reading can coexist with a growing economy.
What does a PMI of 50 mean?
It means the share of companies reporting improvement exactly matches the share reporting deterioration, so activity is flat compared with the previous month.
What is the difference between the ISM and S&P Global PMI?
Both survey purchasing managers and use the same 50 threshold, but they differ in sample, weighting and release timing. S&P Global also publishes flash estimates and comparable PMIs for dozens of countries.
Does a PMI below 50 mean a recession?
Not necessarily. US manufacturing PMI stayed below 50 for 16 straight months from late 2022 without a recession, because services, a much larger share of the economy, kept growing.
Why does the PMI move markets more than GDP?
It arrives weeks earlier and is rarely revised, so traders use it as the first hard read on the month that just ended.
