According to the latest report 'Catalonia: demographic decline of a multicultural society,' prepared by the CEU Demographic Observatory, affiliated to the Center for Studies, Training, and Social Analysis (CEU-CEFAS), the immigrant population now contributes around 50% of the babies born in Catalonia, a percentage that has been increasing over the years. In Barcelona, 53.4% of young men were born abroad. Just a year ago, 46.6% of the male inhabitants of the Catalan capital aged 20 to 39 were born in Spain.

Catalonia is one of the Autonomous Communities with the highest immigration rate. A significant part of the new Catalans are children of Hispanic American, African, or Asian parents. According to this report, the deaths of Spaniards born in Catalonia have exceeded by 280,000 the births of mothers born in Spain in the last 15 years; twice as many Spaniards die as are born, but with foreign immigrants, the balance is the opposite, with six births for every death. With very low fertility, the Catalan population of origin is destined to diminish and to be increasingly aged (more than 25% of it is already 65 years old or older). Currently, the number of children per Catalan woman is very low, so that each new generation of Catalans is 40% to 45% smaller than the previous one. 

In demographic projections, there are usually two scenarios of special interest: the base scenario (the central forecast) and the "zero migration" scenario. The difference in projected population between both scenarios mainly comes from the arrival of new immigration plus their descendants in the country or region of arrival. According to the base scenario, in 2050 there will be 8.75 million inhabitants. In 2100, 9.3 million, which would mean a population growth due to massive foreign immigration. In a scenario without migrations, in 2050 there would be 6.85 million inhabitants, compared to 4.3 million in 2100—a decrease of almost half of the current population. The difference between both scenarios implies 1.9 million more immigrants and descendants by 2050, and 5 million more by 2100.

On the other hand, as 50% of the current babies in Catalonia are offspring of foreign immigrants, that would mean that of the 4.3 million inhabitants of 2100 in the scenario without (new) migrations, at least 2.1 million would be people with foreign family roots. That is to say, if there were no crosses between Spaniards and immigrants, there would be from 7.1 to 7.2 million descendants of current and future immigrants, and only 2.1 to 2.2 million Catalans of Spanish origins, including those we would call "native Catalans" and offspring of Spaniards from other regions.

In some Catalan areas, multiculturalism reaches very high levels that in the past would have seemed unimaginable. In towns such as Salt, Vic, Figueres, Palafrugell, Martorell, Manresa, Mollerussa, and Reus, the multicultural mosaic reaches extremes that would have been unimaginable just a couple of decades ago. In 2022, almost 50% of those born in Catalonia had at least one parent born outside of Spain, a percentage that was greatly exceeded in the province of Girona. 

According to this study, it is worth noting that Catalonia has gone from attracting Spaniards from other regions to having a net emigration of Spaniards (including native Catalans). It attracted a lot of Spanish population from other regions between the end of the 19th century and the end of Francoism, but for decades, it has lost its appeal to Spaniards from other regions, despite having more economic strength than the Spanish average. Specifically, in the period 2015-2022, Catalonia had the most negative interregional migratory balance in all of Spain. In this type of flow, it can be expected that regions with higher per capita income will attract national population and vice versa. This assumption is clearly fulfilled in cases like Madrid, Extremadura, or Andalusia, but not in Catalonia or the Basque Country.

The report also notes that Spanish is still the majority language in Catalonia, bolstered by the abundant Hispanic American population, which, including their children born in Spain, already represents 11% of the total Catalan population. However, as of January 1, 2023, among Western Europeans residing in Spain, the number of children under 15 years old per 1,000 25 to 54-year-old Western Europeans was 30% higher in the Community of Madrid than in Catalonia. This fact could be due to language immersion in Catalan schools. 

In addition, the report shows that the most common surnames in all of Spain are also the most common in Catalonia. As of January 1, 2022, 17.6% of the population carried one of them as their first surname. In the rest of Spain, 25.7%. This would indicate a coincidence of 17.6/25.7, that is, 68.4% of the surnames of the Spanish + Hispanic American immigrant population in Catalonia would be of "generic Spanish" type, and the remaining 31% are native Catalan surnames or have other origins.