I've done the analysis and for the simpler analysis, it's 100% on average (some get afflicted more than once, some not at all, most once, with an average of one).
So, for an AN incidence of 1 diagnosis/100,000 people/year (it's a bit more than this for AN), for people living 100 years (it's a bit less for this and between the two, we're about right), we have:
* The chance of someone being diagnosed with an acoustic neuroma in their lifetime is 1/1,000. That is, 0.1%.
* The chance of an individual, that you meet at random, being diagnosed with an acoustic neuroma in the past year is 1/100,000. That is, 0.001%.
* The age distribution does not matter. Acoustic neuromas can occur at any age without affecting the incident rate. All that matters is that you have a 0.1% chance of diagnosis in your lifetime and that your lifetime is 100 years.
Please challenge this. Once it's finalized, I'll move onto prevalence, which is what is the chance of someone getting an acoustics neuroma in a lifetime, both diagnosed and undiagnosed. This will be taken from published postmortem studies.