I've been doing this almost since the day I started appraising because it was logical. None the MLS systems I use started making this data available (as an automatic MLS reporting item) until a couple of years ago.
I had a large handfull of sale and listing printouts. All I did was divide the sale price by the list price and scribble the calculation on the sheet. 105%, 97%, 96.4%, 91%, etc., etc. I used the most logical percentage for the listing comp.
Please do tell us how you determine the "most logical" percentage. Would that be the median, the mean, the most common percentage or the one that you liked the best for that particular listing comp?
Almost any property will sell if the price is right. If the price is wrong it will either sell too fast or take too long. That's why there is a wide variance in Sales price to list price. That's why you can't just make casual adjustments to listings for this. You have to track down the listing history and hunt for price changes and interview agents to find out what's going on (tenant is uncoopertive, back yard is a mess, seller refuses to list at a reasonabel price, agents won't bother showing the property because the seller refuses to list at a reasonable price, etc., etc.)
This 1004MC monkey business can cause an misleading appraisal report if we're not careful. IMO of course.