If you're wondering why 1004, a seemingly random number, is so close to the top of the list -- something that the author does not investigate in any detail -- my guess is that the database he used contains some major leaks from Korea. 1004 is a fairly popular password there, because it is one of the few 4-digit numbers that sound like actual words in Korean. 1004 sounds like "angel" (cheonsa).
So if you're actually trying to break into people's accounts, it would be advantageous to know your victims' ethnicity. It's quite likely that cards stolen in Koreatown will have a different distribution of PIN numbers than those stolen in Chinatown.
Interesting. When you say 1004 'sounds like angel', do you mean saying 'one thousand and four' in Korean sounds like cheonsa? or 'one zero zero four'? Or the numbers look like letters than spell out angel?
/ tangent
It's read "one thousand four" in US english. In British english (and in many Commonwealth countries like Australia and New Zealand; not sure about Canada) it's read "one thousand and four", regardless of whether the and is unnecessary or ambiguous.
Admit I don't have strong feelings either way but out of genuine curiosity, why is one thousand four less ambiguous than one thousand and four?
You could argue one thousand four is actually easier to misinterpret because it could easily (although incorrectly) be read to mean "one thousand fours."
For what it's worth, the "and" is mandatory in my language and we manage to disambiguate 100 2/3 from 102/3 by putting a pause between either "hundred" and "and" or "two" and "thirds".
100 2/3 - one hundred ... and two thirds
102/3 - one hundred and two ... thirds
Alternatively, use "plus" instead of "and" in the first case.
Surely that comes from the same language structure which means you wouldn't say beans and eggs and tomatoes and potatoes, you'd say beans, eggs, tomatoes and potatoes e.g. in a list of "and" items you only say and between the penultimate and final items?
So if you're actually trying to break into people's accounts, it would be advantageous to know your victims' ethnicity. It's quite likely that cards stolen in Koreatown will have a different distribution of PIN numbers than those stolen in Chinatown.