Economic growth in the US over the same period was mediocre, with declining productivity, and in Europe, it was anemic.
There is just no evidence that nations which focus on diversity in and of themselves have had better economic outcomes.
Now it does make sense that if you are in a large multi-ethnic society then you will be at a disadvantage if you only hire from one group, since good people are hard to find, so why limit yourself to just a small subset of the population. This is less important for a small company than a large company that really needs to cast a wide net. So not intentionally excluding subgroups of your population makes economic sense.
But I'm not aware of any evidence that being more diverse than your population will improve outcomes.
This is not true. In the case of Japan, so long as an employer there is willing to sponsor your visa, you'll have no problems immigrating there or becoming a permanent resident.
Hungary has successfully created incentives to raise their birth rates for example. The Hungarian government doesn't want to rely on mass immigration to sustain the country's population it seems. You don't need imported diversity for more jobs - you can just create very "un-diverse" people yourselves, which will work those jobs once they've grown up.
If other Western nations like the US would seriously get behind an idea like this, with all the power of the media and various propaganda outlets, they, too, would quickly see a cultural shift towards rising birth rates. Unfortunately the people in control don't want this to happen.
Whether ever-continuing growth to chase the 0.3% higher GDP each year is desirable, is another topic though.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and sticking to the rules when posting here, we'd be grateful.
How are you expected to add thousands of jobs if Asians, Indians need not apply?