In 20 years I have never been on a team that didn't have twice as much work as we had people to do it.
Businesses are not magically efficient
Businesses are not magically efficient
Many businesses are not bottlenecked by processes that are computer based.
Obviously, there are limits: I’m not sure what my local grocery store or bus line would do with 100 new workers, but I have no doubt they could put a few people to work right away.
If your existing labour suddenly gets more productive, there's still a trade-off between cost and benefit to be made. And it would be a great coincidence if the optimal trade-off were exactly at the same headcount as the old trade-off under the old productivity figures.
It's more likely that the optimal trade-off for the business under the new conditions is at some other headcount.