Maybe data in the others copmpanies tables is well organized . For example , strings like street names can be "compressed" to very short strings by using some "smart" functions, like those used for encryption and compression in archives . In cases where are many long character fields compression can be very strong . But this methods slows speed in working with records . If there are 3 fields with 30 length and they are reduced to 10 each, to 35 million records means (30-10)bytes*35000000*3=aprox. 2GBytes (!) less harddisk space occupied . Did I calculate correctly ?!!!
If you saw files like d00, d01, maybe the other companies break data in many files. For example, every district has a different file and these names are memorised in a file to be known where to search data .

Mihai