The survey was complied and published by a private foundation called 自動車検査登録情報協会 (Jidoushakennsatourokujyouhoukyoukai [Jidousha-kennsa-touroku-jyouhou-kyoukai], Automobile Inspection & Registration Information Association). "Household" used in this survey is based on addresses used on car registration/inspection. It is not based on 戸籍抄本・登録 (koseki shouhonn/touroku). First, even in Japan a private organization such as this does not have an access to information to like 戸籍 (koseki). Also, problem with using information from 戸籍 is that address listed on 戸籍 is 本籍地 (honsekichi) and 戸籍 does not list current home address, 本籍地 (honsekichi) comes form parents (usually father, unless parents choose mother's 戸籍 at marriage) 戸籍 which likely came from grandfather's 戸籍, etc. Only way to change 本籍地 (honsekichi) on 戸籍 (koseki) to represent current address is to 離籍 (riseki) which removing yourself from your family's 戸籍 (koseki) then your new 本籍地 (honsekichi) on 戸籍 (koseki) will show the current address of the time of 離籍 (riseki). But when you move later in your life 本籍地 (honsekichi) on 戸籍 (koseki) will not change.

Anyway, this survey by 自動車検査登録情報協会 (Jidoushakennsatourokujyouhoukyoukai [Jidousha-kennsa-touroku-jyouhou-kyoukai], Automobile Inspection & Registration Information Association) uses address on the auto registration to determine the "household" this survey includes non-Japanese owning car in Japan.