Your example anticipates a huge growth in productivity, which is a factor in GDP; in that case, the stock market is a forward indicator of anticipated GDP.
Which, if so, still doesn't allow it to grow infinitely out of proportion to GDP, unless the time horizon keeps changing or the anticipation of the future gets steadily farther away from reality.
So you mention in the eras it that it outpaces GDP... I've consistently had the message drilled into me that in the long term (20+ year horizon), stocks will return something like 7-10%, while of course, nobody would expect GDP growth anything like that (outside of a rapidly industrializing environment where productivity is rocketing upward, like China).
Which, if so, still doesn't allow it to grow infinitely out of proportion to GDP, unless the time horizon keeps changing or the anticipation of the future gets steadily farther away from reality.
So you mention in the eras it that it outpaces GDP... I've consistently had the message drilled into me that in the long term (20+ year horizon), stocks will return something like 7-10%, while of course, nobody would expect GDP growth anything like that (outside of a rapidly industrializing environment where productivity is rocketing upward, like China).
An era is not forever, so...