The ISM Manufacturing Index is a monthly report released by the Institute for Supply Management (ISM) that provides a gauge of activity and performance in the manufacturing sector of the US economy. It is based on a survey of purchasing and supply executives across the country and measures factors such as new orders, production, employment, supplier deliveries, and inventories. The index is considered an important leading indicator of the health of the economy, as the manufacturing sector tends to be sensitive to changes in business cycles. A reading above 50 indicates expansion in the sector, while a reading below 50 indicates contraction.