Data Genetics crunched the numbers:
In my dataset the answer is 8068 with just 25 occurrences in 3.4 million (this equates to 0.000744%, far, far fewer than random distribution would predict, and five orders of magnitude behind the most popular choice). Warning: Now that we’ve learned that, historically, 8068 is (was?) the least commonly used password 4-digit PIN, please don’t go out and change yours to this! Hackers can read too! They will also be promoting 8068 up their attempt trees in order to catch people who read this (or similar) articles.
Other passwords to avoid? Definitely "1234," used by nearly 11%:
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 right. A staggering 26.83% of all passwords could be guessed by attempting these 20 combinations! (Statistically, with 10,000 possible combination, if passwords were uniformly randomly distributed, we would expect the these twenty passwords to account for just 0.2% of the total, not the 26.83% encountered)