I know that at the Arkansas Air Museum in Fayetteville, Arkansas, our
donation rate ran pretty at $.33 a head from month to month.  On some very
good months, it would climb up to $.50 a head. So you can perhaps use that
as one yard stick for one of your measurements.

When the local National Historic Site here in Oregon began charging an
admission fee ($2.00/head), I know their visitorship levels dropped between
25% and 35%. So perhaps that will give you another yardstick.

Here's you might want to consider. A good number of the people you bring
into the museum will visit your gift shop and perhaps consider buying a
membership while they are in there. If you charge an admission fee, you're
cutting this pool of museum gift shoppers and possible members down by at
least a quarter.

So you'd also want to consider what you might lose in memberships and gift
shop income when you're looking at what you might make by charging
admission. If the figures are close, perhaps you could bring in the same
amount of money by taking a few extra steps to increase your free museum
visitorship.

Just something to think about.

Thomas E. (Pete) Jordon