You have not cited a single source that indicates 90% of italians returned to Italy. This is not borne out by ANY population or immigration figures I have seen.
You may be refering to golondrinos- Italian workers who went back and forth between Italy and Argentina every year- but that number peaked at about 30,000 per year in 1912 or so- a time when there were well over a million italian immigrants in Argentina.
"In Argentina the famous golondrinas (’swallows’) had traditionally fulfilled much of the demand for seasonal farm labor. These workers, who were primarily Italian, used cheap steerage-class steamship fares to travel back and forth between Itily and Argentina to work in the harvests of both countries, which took place at roughly opposite times of the year. At its height during the 1908-12 period, golondrina migration brought between 30,(XX) and 35,000 laborers to Argentina annually. Mark Jefferson*^ compared them with European Opera singers, who also habitually sojourned in Argentina during the Northern hemisphere summer. Some golondrinas, he found, had made the trip seventeen times or more. A diligent seasonal worker could easily take the respectable sum of 150 Argentine gold pesos back to Italy; some netted nearly double that amount^*." (Solberg 1987:95-96)
There is no record anywhere of millions of italians returning to Italy.
Italian immigrants came, and stayed, in Argentina every year thru 1930.
By the millions. As I stated before, a certain percentage of immigrants always return home- usually around 10%. the percentage of italians returning could be higher- please, cite figures.
But the fact that Argentina is currently about 65% of Italian heritage means that most italian immigrants stayed, and had families.
"As Germani (1970:299) demonstrates, from 1890 onwards, immigrants took up mainly non-agricultural occupations after arrival."
It was true that earlier in the 19th century, many italians were rural agricultural workers- but in the 20th century, Buenos Aires had a large italian immigrant population- Vasena, who was ITALIAN, had 2000 mostly italian employees at his foundry and blacksmith shop, where the strike and violence started the Semana Tragica. That was merely one of many factories and workshops where most of the urban, non-agricultural employees were italian immigrants who never returned to Italy in the first 20 years of the 20th century.
The entire european immigration in the Peron years, say, 47 to 57, was well under 1 million people, and the total number of Italian immigrants under Peron was around 380,000. Not nearly enough to make 50% of Argentina Italian.
"Between 1947 and 1957 about 840,000 Europeans came. 610,000 stayed permanently, and of them 388,000 were Italians. The highest immigration levels were recorded during the Peronist boom years of the late forties. Already by 1952, numbers were falling again and by 1960, and from then onwards, return migration outnumbered new immigration (Roncelli 1987:113-115, Nascimbene 1987:104)."
this is another easily findable paper online, which is copiously footnoted, and refers to many standard works on immigration, in both english and spanish.
http://etheses.lse.ac.uk/1287/1/U062673.pdf
Y