[bnegreve]

It is not, because at least 3 factors of the equation are incredibly difficult to estimate. About as difficult as estimating the probability of an alien encounter. So the equation is basically useless.

[mikeash]

And what’s the term for a figure that’s hard to estimate but which you guess at anyway? An “assumption.”

[bnegreve]

Yes, and in this case, an unreasonable one.