"Do we know if there is a "no egg" rarity tier? (Question and hypothesis)"

#PokemonGO: I was looking for information about the rarity tiers in 7km eggs in the research results published by thesilphroad, and my attention was drawed again by the strange numbers used in the odds. For example, the odds of getting an alolan vulpix in summer were 1/29. Being the tiers based on a base two exponent (1/2/4/8...), I would expect odds being something like 1/64 or 1/32. But instead, we get 1/29 or 1/21, changing every time the pool changes. Then it struck me: What if there is a "no egg" rarity tier, the odds of "not receiving an egg", that added to the hatching pool summed that base two exponent one would expect?For example, in the summer the total odds of all the rarity tiers in 7km eggs were 29/29. That could mean the odds of not getting an egg from a present were 35/64, and the odds of getting something from the egg pool would be 29/64. That is, from a single present in summer there would have been 1/64 odds of getting a vulpix.The implication of this hypothesis would be that when the egg pool changes, the odds of getting an egg or not also changes. Something that would be along the lines of some comments about egg drop rates decreased or increased every time there are changes in the egg pool.This hypothesis would be pretty easy to confirm or deny by knowing the egg drop rates. And so here is the question: There has been any research about the egg drop rates? Not the rates inside the eggs, but the chances of "getting" and "not getting" an egg.TL;DR: I have an hypothesis about the egg pool, but I need to know if there is any research about the rates of "not getting" an egg from a present.EDIT: It seems there hasn't been any research about this, so I will do some by myself. If I have some minor results that go in the direction of this hypothesis, I will then ask how to do a more serious research.EDIT2: The Silph Road Research Group has been investigating this, but has not published results. So I will wait for those results and meanwhile I will make a little research by myself. via /r/TheSilphRoad http://bit.ly/2B5Hj7x