where can i find statistics on whether people leave or drink the milk
after finishing all the cereal in the bowl?

if there are statistics on this, methinks our obsession with stats has
gone round the bend

Hmm, perhaps you could take an informal poll and extrapolate the
results over a population?

While I have to agree with the first comment left here, I can suggest
a strategy for taking such a poll.  To get a fairly large sample, you
need to observe lots of people eating breakfast.  I suggest you take
yourself for a overnight stay in a fairl-sized and busy hotel and stay
for breakfast,  Choose your vantage point and make notes while other
guests come and go.

I agree that the personal statistical observation might be the way to
go.  However, I think that people eating cereal in public might not
turn their bowl up and drink the milk (I hope manners extend that
far!) when they might at home.  I suggest an informal survey mailed or
emailed to everyone in your address book.  You might want to ask about
everyone in each family, as children might or might not be as big a
milk drinker as an adult.  (Here's one stat for you:  me, 34-yr-old,
single, Caucasion female...I absolutely drink the milk, especially if
I've just finished a chocolate cereal!)  Good luck with this.  It
sounds like fun.