Alpha Acid loss in whole hops?

I recently got a "pound" of whole Columbus hops from HopsDirect.

As quickly as possible, I put 1 oz portions in ziplocks, squeezed every possible bit of air out, put them all in a jumbo ziplock, squeezed every possible bit of air out of that, and put it into the deep freeze (which we keep on the coldest setting).

I know that one always loses some AA to oxidation with whole hops. Anyone have a reasonable estimate of what percentage that loss is? This batch was labelled 16% AA (!!!).

I know it's kindof anal, but I'd like to have a decent guess what the actual AA is for computing IBUs.

I know ProMash and BeerSmith both estimate hop degradation after you input storage temperature and time (actually, I think they give a degradation chart with months on one axis). However, I don't know the actual formula. I think your storage technique is quite sound.