A nationalist activist during World War I, he became noted for his pioneering research into the biostatistics of Transylvania and Banat regions, as well as a promoter of eugenics and social interventionism.

[1] As noted by scholar M. Benjamin Thorne, the Manuilă family also harbored racist prejudice against the Romanies (Gypsies), which may have shaped Sabin's political stances.

[27] In 1929, he entered Gusti's Romanian Social Institute, and that year, together with five other doctors, he participated in a Gusti-coordinated monograph-writing campaign at Drăguș village in the vicinity of Făgăraș.

[30] Supervised by Gusti and funded by the Rockefeller Foundation, Manuilă and his wife also created a Bucharest School of Social Work, which doubled as an institute for the propagation of eugenic ideals.

In 1929, he put out the treatise Evoluția demografică a orașelor și minorităţilor etnice din Transilvania ("The Demographic Evolution of Cities and Ethnic Minorities in Transylvania"), which earned him another Academy prize.

[33] He made projects about population exchanges between Greater Romania and its various neighbors, with the goal of discarding "elements with a centrifugal tendency" and keeping "ethnic purity", and even proposed the colonization of his native Crișana with Romanians from Hungary.

[34] Moreover, Manuilă campaigned for the adoption of social welfare and biopolitical laws that, he argued, would curb emigration from Romania[35] and promote the consolidation of a Romanian urban society.

[39] From 1927 to 1930, he was a high-ranking civil servant within the Labor, Health and Social Protection Ministry,[5][6] and was Undersecretary of State in a PNȚ cabinet, under Prime Minister Iuliu Maniu.

[45] Returning to the Institute of Demography and Census, Manuilă helped Gusti organize another expedition, this time to his native Sâmbăteni (1934), and studied first-hand the region's depopulation.

[48] He also insisted on his old idea of "eradicating" the Hungarians of Crișana and bringing in their stead Romanians stranded across the border in Hungary, and demanded a strict policy of linguistic discrimination in Transylvania-proper.

[49] Nonetheless, Manuilă toned down the racialism of other eugenicists, who wanted the Székelys and their Csango relatives to be counted as separate from Hungarians, based on claims that both of the former had Romanian ancestry.

[54] Dealing with the Great Depression, his articles of the time discuss the "overpopulation" of Romania's universities as a cause of white-collar unemployment, proposing a government selection of the human capital.

With Mihail Manoilescu and other Foreign Affairs officials, Manuilă attended the meeting in Turnu Severin, where the Romanian side first took into consideration population exchanges between Romania and Hungary.

Manuilă and his staff were directly subordinated to the Conducător, "substantiating governmental policy decisions" and, after Romania's entry into the conflict as a Nazi ally, making demographic projects in view of a future peace.

In his 1940 article about "racial commands", where he proposed to create a "Superior Council for the Protection of the Race",[67] Manuilă insisted that the Jews were a largely harmless community, both self-segregated and endogamous.

[72] Manuilă soon began work on a new census, "a giant, extremely complex operation"[72] which was intended to give added weight to Romania's claims on her neighbors.

[76] In late 1941, with Romania's participation on the Eastern Front as a German ally, Manuilă again proposed, in his memos to Antonescu, a population exchange, meaning to solve the issue of Northern Transylvania.

She was also to cede much of Hotin, Storojineț, and Cernăuți counties to a Nazified Ukraine, and some western areas (including Salonta, Oradea, and Satu Mare) to Hungary.

[83] This measure was supposed to enforce Romania's "ethnic homogeneity", and was presumably influenced by Manuilă's confidence in Moldovan's eugenic movement,[84] but did not, in fact, call for the physical elimination of either community.

[65] Later that year, Transnistria Governor Gheorghe Alexianu ordered Manuilă and Făcăoaru to carry out an anthropometric study of the Romanian soldiers, to gather evidence on possible Jewish exogamy.

[89] Nonetheless, one of the memos stands as a historical premiere, since Manuilă made official claims about a "Gypsy problem", again describing the Romanies as a "dysgenic" threat,[90] "social and national non-values, and a racial hazard".

During the events, Golopenția and his men occupied the building housing Radio Bucharest,[38] while Manuilă, from his home on Schitu Măgureanu Boulevard, ensured communications between the PCdR and Maniu.

In his December 1944 interview with the Jewish magazine Curierul Israelit, he asserted: "The adoption of racial laws constitutes a great aberration in the mind, is not congruent with this century, and is alien to the traditions of the Romanian nation.

[96] With Georgescu-Roegen and the state carrier inspector Max Manolescu, Manuilă considered a plan to escape from Romania by plane, but this was thwarted by police during a routine checkup.

As noted by scholar Johanna Granville, this reply omitted to mention that the overthrow of fascism had in fact resulted in Northern Transylvania being returned to Romania.

[118] Professionally, Manuilă was employed by Stanford University Institute for Food Research, where he published a monograph on The Agricultural Economy of the Danubian Countries: 1935–1945, then as a Counselor for the United States Census Bureau.

[120] During the 1950s, he also completed work on demographic histories of the Romanian Jews (Regional Development of the Jewish Population in Romania in 1957, Populația Evreiască din România in 1958).

[121] These brought him close to Wilhelm Filderman, the exile Jewish Romanian political activist and RNC affiliate, who helped him obtain raw data.

[65] In September 1963, Manuilă attended the 20th International Congress of Sociology, in Córdoba, Argentina, where he presented a paper on wartime demographics in Romania, noting the increase of living standards in the 1960s.

[126] Controversially, in the mid-1990s Manuilă's studies on minority populations were included in works of Holocaust revisionists Kurt Treptow and Larry Watts, alongside fabricated quotes from Filderman, in what was read as an effort to induce doubt about Antonescu's antisemitic crimes.