alt Hacker NewsIt's not as if Japan (or any other country, for that matter) doesn't already have immigration restrictions. Japan uses a points-based merit system for permanent residence [1], not unlike the criteria you suggested. Just to give an example, having a PhD and speaking Japanese at an N1 level (~equivalent to B2 CEFR) is barely sufficient to qualify (unless you're older than 30, in which case it won't be).
The more interesting question to ask is: Why has Japan decided to tighten immigration requirements now? But in my opinion the answer is rather obvious, especially when you consider the current Prime Minister's nationalistic beliefs: It's much easier to blame foreigners for insufficient welfare, ailing infrastructure, etc than to actually improve welfare, infrastructure, etc.
Also, the example of "a 68 year old alcoholic high school dropout with multiple violent criminal convictions" is rather ridiculous. You're arguing a strawman. It's already impossible for such a candidate to immigrate almost anywhere barring some other exceptional circumstances.
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[1] See here, eg, to see how you would fare: https://japanprcalculator.com/
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My example is ridiculous, but it was the easiest way to point out the fallacy that "you can never measure which [immigrants bring value or cause problems]. You clearly can.
And no, that 68 year old alcoholic is free to pass into America under Democrat administrations and tens of thousands have. They technically are illegal, but if you selectively enforce immigration laws and offer things like asylum/refugee status without any checks or balances, the net effect is still the same.
Returning to Japan, as the other commenter pointed out, your PhD example is someone that qualifies for expedited permanent residency, a particular subset of migration that Japan has (correctly) decided to encourage.
This is misleading at best, straight up false at worst.
The points-based system is used to allow you to apply for a PR _on an accelerated timeline_; not apply at all.
Having 70/80 points lets you apply for a PR after being a resident for 1/3 years respectively; you can apply without any points after living here for 10 years.