Firms locate mainly or exclusively within or outside the port perimeter. Based on the available information, we find that only 26.5 per cent of the firms are located exclusively within the port perimeter, 31.7 per cent are located also within the port perimeter and 41.9 per cent are located outside the port perimeter. This indicates that one cannot understand what a port is, only by looking at what happens within its area, as the literature on port regionalization suggests.