Immigration quotas in the 20s targeted “undesirable” nationalities to stem the inflow of low-skilled Eastern and Southern Europeans; this study measure effects in inventions and scientific production

Moser, Petra and San, Shmuel, Immigration, Science, and Invention. Lessons from the Quota Acts (March 21, 2020). SSRN: http://dx.doi.org/10.2139/ssrn.3558718

Abstract: Immigration quotas in the 1920s targeted “undesirable” nationalities to stem the inflow of low-skilled Eastern and Southern Europeans (ESE). Detailed biographical data for 91,638 American scientists reveal a dramatic decline in the arrival of ESE-born scientists after the quotas. Under the quotas, an estimated 1,165 ESE-born scientists were lost to US science. To identify effects on invention, we use k-means clustering to assign scientists to unique fields and then compare changes in patenting by US scientists in the pre-quota fields of ESE-born scientists with changes in other fields where US scientists were active inventors. Baseline estimates imply a 68 percent decline in invention. Decomposing this effect, we find that the quotas reduced both the number of US scientists working in ESE fields and the number of patents per scientist. Firms that employed ESE-born scientists experienced a 53 percent decline in invention. The quotas’ effects on invention persisted into the 1960s.

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Naturalization data indicate a dramatic decline in the arrival of new ESE-born scientists after the quotas. Until 1924, arrivals of new ESE-born immigrant scientists were comparable to arrivals from Northern and Western Europe (WNE), who were subject to comparable pull and push factors of migration.1 After the quotas, arrivals of ESE-born scientists decline significantly while arrivals from Northern and Western Europe continue to increase. Combining data on naturalizations with information on scientists’ university education and career histories, we estimate that 1,165 ESE-born scientists were lost to US science under the quota system. At an annual level, this implies a loss of 38 scientists per year, equivalent to eliminating the entire physics department of a major university each year between 1925 and 1955. For the physical sciences alone, an estimated 553 ESE-born scientists were lost to US science.

To estimate the effects of changes in immigration on US inventions, we compare changes in patenting per year after 1924 in the pre-quota fields of ESE-born US scientists with changes in patenting in other research fields in which US scientists were active inventors before the quotas. This identification strategy allows us to control for changes in invention by US scientists across fields, for example, as a result of changes in research funding. Year fixed effects further control for changes in patenting over time that are shared across fields. Field fixed effects control for variation in the intensity of patenting across fields, e.g., between basic and applied research.

Baseline estimates reveal a large and persistent decline in invention by US scientists in the pre-quota fields of ESE-born scientists. After the quotas, US scientists produced 68 percent fewer additional patents in the pre-quota fields of ESE-born scientists compared with the prequota fields of other US scientists. Time-varying effects show a large decline in invention by US scientists in the 1930s, which persisted into the 1960s. Importantly, these estimates show no preexisting differences in patenting for ESE and other fields before the quotas.

Special case of Paul Erdős:

A case study of co-authorships for the prolific Hungarian-born mathematician Paul Erdős illustrates how restrictions on immigration reduced collaborations between ESE-born scientists and US scientists. Erdős moved to the United States as a post-doctoral fellow at Princeton, and became a professor at Notre Dame, travelling and collaborating with many US scientists. As a Hungarian citizen, however, Erdős was denied a re-entry visa by the US immigration services in1954, and not granted re-entry until 1963. To examine how these denials affected Erdős’ collaborations with US scientists, we collect the location of Erdős top 100 coauthors at the time  of their first collaboration. These data show that Erdős’ collaborations shifted away from the United States when he was denied re-entry. Between 1954 and 1963, 24 percent of Erdős’ new co-authors were US scientists, compared with 60 percent until 1954. These patterns are confirmed in a broader analysis of patents by co-authors and co-authors of co-authors of ESEborn scientists, which indicates a 26 percent decline in invention by scientists who were directly or indirectly influenced by ESE-born scholars.