Markit and in association with PMAC, is based on data compiled from monthly replies to questionnaires sent to purchasing executives in over 400 industrial companies. The panel is stratified geographically and by Standard Industrial Classification (SIC) group, based on industry contribution to Canadian GDP. Survey respondents reflect the change, if any, in the current month compared to the previous month based on data collected mid-month. For each of the indicators, the 'Report' shows the percentage reporting each response, the net difference between the number of higher/better responses and lower/worse responses, and the diffusion index. This index is the sum of the positive responses plus a half of those reporting 'the same'. Diffusion indexes have the properties of leading indicators and are convenient summary measures showing the prevailing direction of change. An index reading above 50.0 indicates an overall increase in that variable, below 50.0 an overall decrease. All data are seasonally adjusted. Markit do not revise underlying survey data after first publication, but seasonal adjustment factors may be revised from time to time as appropriate which will affect the seasonally adjusted data series.