ISM Index (Institute of Supply Management's index, former NAPM — National Association of Purchasing Managers) is the index of business activity.
ISM figures above 50 are usually considered as an indicator of expansion, while values below 50 indicate contraction. Typically, when ISM approaches 60 investors begin to worry about possible economic overheating, inflation increase and the corresponding measures (raising rates) by the Federal Reserve Bank. Figures below 40 entail talks about recession.
ISM is released just before unemployment data are announced, and is often used to refine data by Bureau of Labor Statistics.