A monthly report based on a national survey of purchasing managers that tracks month-to-month changes in business activity in service industries. Like the PMI index, the ISM report on services establishes a neutral point at 50 percent. An index reading above that number represents growth and anything below it represents a decline. The report is released by the Institute for Supply Management on the third business day of each month and is based on data from the prior month. The data are available at a number of financial information Web sites.