The PMI monthly Composite Reports on Manufacturing and Services, released by Markit Economics, are based on a large number of business executives in private sector manufacturing and services companies. Data is usually released on the third working day of each month. Each response is weighted according to the size of the company and its contribution to total manufacturing or services output accounted for by the sub-sector to which that company belongs. Replies from larger companies have a greater impact on the final index numbers than those from small companies. Results are presented by question asked, showing the percentage of respondents reporting an improvement, deterioration or no change since the previous month. From these percentages, an index is derived: a level of 50.0 signals no change since the previous month, above 50.0 signals an increase (or improvement), below 50.0 a decrease (or contraction).