Another crucial aspect is clustering : the issue is completely different when the overflow hotels are across the street (as one in Yokohama) and in Buenos Aires (where the nearest overflow hotel is 1.7km away). If selecting locations that can host everyone in one hotel is hard, surely it is easier to find places with a cluster of reasonably close (walking distance) hotels to a large-enough conference center. I think this could take a higher priority in the selection process, for the future. All the best, Julien.