A monthly survey of purchasing managers in industrial companies that records changes in items such as orders, employment, inventories and prices, compared with those of the previous month. It is expressed as a number, with 50 regarded as neutral (ie. the same number of respondents reporting increased activity as there were reporting decreased activity). Figures above 50 indicate growth and below 50 contraction. The index is regarded as a leading indicator of economic activity, but methodology varies from country to country.