[0xffff2]

I think for the purposes of this question, "IPO whose S-1 gets posted to HN" is a good definition. No need to overthink it.

[jtsiskin]

Yes, this is exactly what I meant. It’s just missing the fact that the popularity of posting S-1’s in general might be changing so charting the # of posts may be different than the real # of “tech ipos”