PMI (Purchasing Managers' Index): the index above and below 50

What it is

The PMI is an index built from surveys of company purchasing managers. A value above 50 indicates expanding activity, below 50 contraction. There are manufacturing and services PMIs, and a composite index.

Who publishes them and when

S&P Global publishes the "flash" PMIs in mid-month for the eurozone, the UK and the US; in the US there is also the ISM index, published at the start of the month at 10:00 New York time. They are among the first data of the month and are therefore closely watched.

How to read it

• The 50 threshold matters but so does the change from the previous month
• The sub-components (orders, employment, prices paid) anticipate the picture
• The surprise against the forecast is what moves the price

Impact on markets

They are leading indicators of the economy: a better-than-expected PMI supports the currency and equity indices; a worse one increases fear of a slowdown.