Why isn't perpetual high unemployment inevitable?

[Mr Khan]

richardhutnik said:

Mr Khan said:
Oil will crash, 2 billion of us will starve, and most of the rest will go back to work in the farms

But seriously, the market should correct against that in the long run. If enough people become unemployed and the demand for manual labor drops low enough, employment will go back up, unless those losses come primarily from the minimum-wage sector, but no-one really makes a living off such employment anyway

Why would employment go back up, unless businessed have a demand for more labor?  If all sectors are automated so that it isn't needed, then where are people employed into?

Really nightsurge made a better reply than i did. New sectors will always emerge that demand manual labor. Who watches the watchers, who builds the automated machines? As more services become transferrable, more people can be employed meeting the world's demands, say, for something more complicated than the average Indian can do, call centers will increase in volume. We're going to need lots of people for the inevitable infrastructure swichovers that are coming: universal fiber-optic broadband, systems to meet the electric car economy or the hydrogen economy, plants to process algae and kelp biofuels to supplement the loss of fossil fuel.

There is a point when pretty much all services could become automated except the creative arts, but if it's a system of sustainable energy, then that'll just be a quasi-Communist utopia like they have in Star Trek, but that's way down the line