To explore the influence of prevalent winds we defined for each child the IP-residence direction, using the above coordinates and wind direction conventions. For example, for an address in the north-east sector (x > x0and y > y0) theIP-residence direction in degrees, clockwise from the north, ranges from 0◦(north) to 90◦(east). We divided the circle into the following sectors: north (22.5◦west of the north to 22.5◦east of the north), north-east (22.5◦to 67.5◦), east (67.5◦to 112.5◦) and other