>> Where would you draw the line instead? 18 months? 3 years?
>
> My doubt is not so much about where to draw the line but what
> I catch with that line i.e., is this a significant statistic
> to gather?
I think Doug would say: that's exactly what the folks at BLS do full time, and they do a pretty good job with it. Your examples point out, in that kind of let-me-think-about-it-for-three-minutes kind of way, that it's a complex issue. And BLS says: let's cut it off at a year, okay? If you haven't actively looked for a job in a year, you aren't unemployed, you're something else.
You can argue whether a year is the right value of N or not, but the line does have to be drawn.
/jordan