From a lengthy and very interesting (if you like math) post at DataGenetics:
I was able to find almost 3.4 million four digit passwords. Every single one of the of the 10,000 combinations of digits from 0000 through to 9999 were represented in the dataset. The most popular password is 1234 - it’s staggering how popular this password appears to be. Utterly staggering at the lack of imagination - nearly 11% of the 3.4 million passwords are 1234 !!!The answer to that last query is at the link, along with much more info.
The next most popular 4-digit PIN in use is 1111 with over 6% of passwords being this. In third place is 0000 with almost 2%. A table of the top 20 found passwords in shown [at the link]. A staggering 26.83% of all passwords could be guessed by attempting these 20 combinations! ...
Looking more closely at the top few records, all the usual suspects are present 1111 2222 3333 … 9999 as well as 1212 and (snigger) 6969 .
It’s not a surprise to see patterns like 1122 and 1313 occurring high up in the list, nor 4321 or 1010 . 2001 makes an appearance at #19. 1984 follows not far behind in position #26, and James Bond fans may be interested to know 0007 is found between the two of them in position #23 (another variant 0070 follows not much further behind at #28).
The first “puzzling” password I encountered was 2580 in position #22. What is the significance of these digits? Why should so many people select this code to make it appear so high up the list?