Isnt it obvious? We can look at indicators such as crime rates of different nationalities, achieved education and income of the immigrant etc. Then we can restrict immigration based on some kind of a point system. This would serve to filter out problematic people while still letting the best immigrate.
Sure, you can do that.
But then you're not going to get as many immigrants as you need, your criteria are incredibly prejudiced (and easily proven to be prejudiced), and you're going to only get qualified people which will cause unrest among your population
because they're going to take previously high-paying jobs away from the natives. See, for example, German immigrants in Switzerland.
And let me ask you a question: If you're going to sort by ethnicity and deducting points for being, say, Romani,
how the **** are you not being racist?
Obviously, the more qualified a job, the less true the rhetoric about "taking our jobs" is. It is simple supply and demand. Low paying jobs are low paying because there is high supply of such people and low demand for them.
So allowing low qualified immigration does steal jobs and only exacerbates poverty, while doing little to help the economy. Since I care about our poor, I am against allowing such migration. On the other hand, high paying jobs are high paying because there is low amount of applicants for the position. Thats why highly qualified migrants are unlikely to steal someones job.
You are incredibly wrong. The more educated and older your population gets, the fewer people are there to do the low-paying, entry-level jobs the economy needs. That's where immigrants come in. They're going to make better money than they would get at home, they get to lay foundations for social mobility for their children, and while they're doing it, do a valuable service for the economy.
If you restrict immigration to qualified people on the other hand
they're going to be seen as a threat by your own natives, because they're going to compete for the high-paying, high profile jobs people want to get. This causes friction.
I found a really nice study about Japan aging with actually relevant numbers:
http://www.ipss.go.jp/site-ad/index_english/esuikei/ppfj2012.pdf
Look at page 31. Currently, working age people make up 63,8% of Japanese population. In 2060, this very important number is going to decrease to somewhere between 52,6% and 48,9%, depending on some assumptions about future fertility and mortality rates.
Now it is undeniably a negative development.
But, is such decrease going to ruin the Japanese economy?
Certainly not. It is just not significant enough to do anything like that.
Look at the table on the next page and the page preceding it. The proportion of young people under working age declines from 13.1 to 6.9 to 11.6%. The proportion of people in retirement age rises from 23% to 35% to 44%. What does that mean? In simple terms, the number of people dependant on state help rises sharply, while the number of people replenishing the workforce falls drastically.
A clear illustration of this can be found in table 1-4. Here, even under the most optimistic of assumptions, the dependency ratio (i.e. the ratio between the working members of society and nonworking ones) rises sharply from 56.7% to
92.7%, meaning that each working person will have to support about 1 nonworking person. Under pessimistic assumptions, 1 worker will have to support 1 nonworker. This is not sustainable
unless we assume that individual productivity can rise to a level where the economy can bear the burden, which is an assumption that is fundamentally unsafe and idiotic to make. As a result, Japan needs to court massive immigration, as this is the only safe option that can rebalance the age pyramid and make sure that the country remains stable.