The Purchasing Managers Index is a monthly survey of business conditions, using identical survey methodology in each country participating in the surveys. Each month questionnaires are sent to a panel of 500 companies, selected to accurately reflect the structure of the construction sector. Data are collected relating to: business activity, quantity of purchases, suppliers delivery times, employment, input prices, future business expectations, housing activity, civil engineering activity, commercial activity, use of sub-contractors, availability of sub-contractors, quality of sub-contractors, rates charged by sub-contractors. Diffusion indices vary between 0 and 100 with a level of 50.0 signaling no change on the previous month. Readings above 50.0 signal an increase on the previous month. Readings below 50.0 signal a decrease. The greater the divergence from 50.0, the greater the rate of change signaled.