>If we don't understand the fundamental limits to any particular kind of trend, our default assumption should be that it will continue for about as long as it h

>If we don't understand the fundamental limits to any particular kind of trend, our default assumption should be that it will continue for about as long as it has gone on already. We can, in fact, easily put a confidence interval on this. With 90% odds we're not in the first 5% of the trend, or the last 5% of the trend. Therefore it will probably go on between 1/19th longer, and 19 times longer. With a median of as long as it has gone on so far. People would confidently cite Lindy's law all the way near the end of a trend. Nothing would stop a Roman saying that just before the Fall. We don't always need to "understand the fundamental limits" to a trend to see where it's going. Just to observe more than a random blind guess about them. I also wouldn't trust the "see how much we're improving" benchmarks of a trillion dollar pre-IPO industry to begin with.