Hop Utilization in the Boil

Does it make that much of a difference in hop utilization whether or not you place your hops in a bag during the boil? Makes for an easier clean-up, but does it effect the bittering of the beer?

I’ve often seen a number of 10% thrown around, but it depends a lot on the amount of hops, size of the bag, and mesh fine-ness. You could use a ROT of 10% reduction and just run with it - you will eventually get a feel for what your system detracts.