On the accuracy of IP geolocation based on IP allocation data

The Regional Internet Registries (RIRs) publish information about all allocated IPv4 and IPv6 address blocks including country codes for each block. This information can be used for IP address geolocation. However, since large IP address blocks assigned to one country may belong to large international organisations spread over multiple countries the accuracy is questionable. With data from May 2012 we compare the IP to country mapping of the RIR data for the whole allocated IPv4 and IPv6 space against MaxMind's GeoIP geolocation database, which has a claimed accuracy of 99.5% [1]. For IPv4 there is a difference for 5% of the address space. This means GeoIP is presumably more accurate, but on the other hand for 95% of the IPv4 address space the mapping is identical. For IPv6 there is almost no difference between the RIR data and GeoIP.