All good points. The age of firms is definitely fat tailed. Further, it is hard to count firm survival (mergers don’t obviously destroy firms, is IBM the same c

All good points. The age of firms is definitely fat tailed. Further, it is hard to count firm survival (mergers don’t obviously destroy firms, is IBM the same company it was, etc). Also what a firm is has changed over time (legally, structurally, etc). It would be interesting to see how many family generation changes family firms can survive. Obviously there are very old firms (some of which are closely tied to the gov: the British Royals, Aramco) but I would guess you have a step-like survival function. Private firms (public or not) can and do build long-lived infrastructure. High voltage power lines are an example (maybe not a great example since they are heavily regulated). Expensive infrastructure has a long-term financing problem because DCF with any reasonable discount rate will essentially turn all earnings 30 years from now into nothing. The persistence of some government that will recognize the debt (or persist some legal entity that will receive the cash flow to service it) makes possible long-term financing. One solution is to make infrastructure cheap but that is hard (and maybe only possible in software).