I guess it depends on what you mean by “enjoyable life”. If it means a continually improving economic situation, then almost all developed economies in the world today are realizing that immigrants are needed- otherwise it's just economic stagnation. Even countries traditionally closed to immigration and the outside world are embracing it. They realize it is impossible to stay competitive in today's world economically (and therefore geopolitically) without immigration.
On June 14, 2024, Japan took a significant step in reforming its immigration policies. A proposed amendment to the Immigration Control and Refugee Recognition Act of 1990—commonly known as the Immigration Law—was passed by the House of Councillors. The ruling coalition of the Liberal Democratic...
www.workjapan.jp
Korea, striving to become a multicultural developed country, still struggles with formulating a comprehensive immigration policy that caters to both Korean needs and immigrants' integration aspirations.
koreajoongangdaily.joins.com
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But perhaps you meant something other than economically?
An enjoyable and safe life includes the general economic welfare of the existing American people. Using South Korea as a hypothetical and thought experiment, suppose that everyone is employed working for or in a business.
As we know, production is a function of land, capital and labor. The "need" (better put is "want") in British Hong Kong was for more land, for India it was more capital, and let's say for South Korea its more labor. Those business people in South Korea may have the land and the capital to start a new or expanded business in order to sell more "widgets" to domestic and foreign consumers but they need workers at a lower labor price.
The capitalist has two options: bring in laborers who will accept lower wages OR go to the laborers. In going to the labor pool of another country the capitalist will use their capital to expand or start their business there, say in Vietnam.
The South Korean business owners (shareholders) will profit regardless. It will make no difference to the lives of South Korean population if they are all ready at full employment. Yes, if the laborers come to South Korea, they and the business owners will also absorb the profits just as the same folks would do so if the businss were in Vietnam. All other things being equal, it does not matter.
What does matter is the effect on the native born South Korean laborer, ie, lower wages for less skilled South Koreans. While the optimal economic efficiency is to let both labor and capital flow freely to optimize production, the distribution of those benefits makes some winners and others losers.
In other words, the added wealth goes to the immigrant laborer and the capitalist, not the laboring class of South Korea. However the social costs are borne by the SK laboring class in affordable housing, and all the other externalities I listed previously
Indeed, the South Korean laboring class would be better off if the South Korean capitalist invested in Vietnam and employed labor there as the capitalists would be equally rewarded but not at the cost of the South Korean worker in either social support or in other social costs.
Finally, a word of caution on statistics. An incerease in immigration that causes an increase in GDP isn't what it seems when it does not increase the per capita GDP. In other words, the immigrant is then barely paying for themselves and no other.
And I would add, this particular excercise makes assumptions about a stable ratio of working and tax payer class and stable sized cohort of retired and non workers. In that case, we have to expand our discussion.