Likelyhood of a good hand after you

[BradleyT]

Let's say we're at a 6 player table and all players at the table will play a hand that's in the top 20% (whichever ranking chart you like). It get's folded around to the small blind who also does not have a 20% hand. Since we know that 5 players did not have a 20% hand does the likelyhood of the big blind having a 20% hand increase much?

This is a common situation in SnGs where it's profitable to push your SB with nearly any two cards into the big blind because you estimate they'll only call with the top 20% of hands - yet it seems like they do have a top 20% hand a lot more than 20% of the time. We had a thread in the STTF forum about this but nobody really knew any mathematical answers about how folded cards increase the likelyhood of a blind having better cards.

Is the first part hard to figure out?