Just out of curiosity, approximately how much would my credit score go down if I don't pay a $500 hospital bill?
There are several issues involved. They include 1) "missed" payments, 2) NON payments 3) severity, and 4) recency.
When you "miss" a payment, your credit score declines "significantly" (a multiple of ten points). The issue has less to do with the amount than with the fact that you now have a "record" of non-payment. If you pay the bill the following month, so that you have no arrearage, you regain most (but not all) of the loss, because you are now "caught up." If a second month goes by without payment, your credit score takes another hit, up to about the 4-6 month range. About now, you are a certified "deadbeat," but if that's the only bill you've missed, there will come a point where your score doesn't go down more.
There's obviously more damage from say, a foreclosure, which is a large amount. Still, if you are foreclosed and start paying your other bills on time, your credit score will rebound, even after about 6 months, because you have "good" credit on those bills partly offsetting your bad.
In any event, as time goes by the impact of a missed payment or even foreclosure itself diminishes. This typically starts to take place some 2-3 years after your last major "event," a lesser amount of time for a small bill.
It will go down some amount the first 30 days it is late, some more the next 30 and some more after that.
How much really depends on what your current history is. If it is your first bill you will be hurt pretty bad, but if you have 30 years of history you will sluff it off after a shorter period of time.
Once you are sent to collection, you can expect another dip. Then the statute of limitations will hit after seven years or so, and your credit score will then start to repair.
One more thing about hospital bills: They may be able to put a lien on your property if you don't pay. I've heard of this happening to people my friends knew. They were trying to sell a house, and an unpaid bill from a hospital had to be settled before they could sell.
So it may be more than your credit rating you have to worry about. One more reason not to skip out on your bills.