Wrong. There are just a handful left (if that) in only Kolkata, mostly by a "legacy" inertia.
International labour statistics has the following as output per worker i.e productivity w.r.t large population countries in South Asia:
This topic page on labour productivity provides access to statistical information including data, methods, publications and more.
ilostat.ilo.org
Bangladesh = 10k
Pakistan = 15k
India = 21k
I won't go into savings or investment rate that will dictate where these trends go this decade. 1 country of these 3 is doing next to nothing on it.
I agree with your post in the more general context.
Higher Labour pricing and vertical internal automation etc will happen if you stop immigration.
The argument becomes how much profit margin is required by companies at various tiers to achieve more productive breakthroughs....as this does need pooling of resources significantly (that becomes ripe target for populist argument to "redistribute" in more throughfare wage consumption).
In any case, the security and law+order is paramount to even having these debates in first place. If there is a large or total breakdown in sufficient intensity, that is an externality that is simply not priced in at all by the immigration (and integration) argument.
