So maybe 10% of all cell phones are primarly used in the "wrong" area?
Out of curiosity, does anyone have a good pointer to the history of how / why US mobile ended up in the same numbering plan as fixed-line?
The US and most of the rest of North America have a fixed length numbering plan designed in the 1940s by the Bell System. They offered it to the CCITT which for political and technical reasons decided to do something else. (So when anyone complains that the NANP is "non-standard", you had your chance.) Fixed length numbers allowed much more sophisticated call routing with mechanical switches than variable length did. For reasons not worth rehashing, there was no possibility whatsoever of adding digits or otherwise changing the numbering plan. So if they were going to do caller pays mobile, they'd need to overlay mobile area codes on top of existing codes, and there weren't enough spare codes to do that. Putting mobiles into a handful of non-geographic codes as they do in Europe wouldn't work because the US is a very large country, long distance costs and charges were important, and they needed to be able to charge more for a mobile call across the country than across the street. (The distance from Seattle to Miami or Boston to San Francisco is greater than Lisbon to Moscow or Paris to Teheran.) In the US, mobile long distance charges have mostly gone away, but my Canadian mobile still charges more for a call to a different province than one to the same city. So rather than doing caller-pays as in Europe, North America does mobile-pays, with the mobile user charged for both incoming and outgoing calls. There turn out to be good economic reasons for that -- European mobile users imagine that incoming calls are "free", but in fact they are very expensive to the caller because the caller has no say in choosing the carrier or the price. For all its faults, the competition in US mobile service drove down prices much faster than in Europe, and US users use more minutes/month than Europeans do. If you want me to call you in the UK, I'm happy to call your landline for 1.3c/min, not so happy to call your mobile at 26c/min. ObNanog: E.164 and VoIP don't make this any easier. R's, John