Birth tourism and base rates

South Orange County social media has been blowing up over a recent report of arrests of proprietors of “birth tourism” businesses, who accepted money from pregnant women, mostly Chinese, in exchange for airplane tickets, lodging, coaching on evading detection, and presumably lamaze classes, in an effort to have their babies become Americans via birthright citizenship. There are plenty of scandalous details in the indictments which seem designed to boil the blood of the still-common OC Republicans, but the rage-sieve that is social media has boiled the situation down to “I KNEW the Asian moms at the Spectrum were suspicious” and “China is playing us for chumps #MAGA”. I thought I would do a bit of simple math to see exactly how likely my neighbors are to be bigots.

My favorite book ever makes two points of relevance for this story: One, that memorable cases are likely to have their prevalences overestimated; and two, that base rates are often ignored when determining the degree of surprise in any given observation. In this case, the valences of the story (foreigners disregarding US immigration law, newcomers refusing to assimilate, Chinese economic exploitation) made it a particularly strong mindworm for OC conservatives, reactivated whenever an Asian woman blocks the aisle at Sprouts with a $2,000 stroller. The neglected base rates arise when every pregnant Asian woman becomes Exhibit A, despite the city having a large resident Asian population, many of whom are pregnant for non-criminal reasons.

Irvine is home to 277,453 people, and 41.2% are of Asian descent. That makes approximately 114,310 Asians. Assuming that the national average of 50.9% female holds true as well, that makes about 58,184 female Asian residents (pace non-binary Asian residents, I am rounding up). Assuming again (probably unreasonably this time) that the age composition of the female Asian population in Irvine is also the same as the US overall, 36.5%, or 21,237, are between the ages of 18 and 44. Using an Internet rando’s back-of-the-envelope calculation, and also assuming that the rates of pregnancy among Irvine residents are the same as the national average, 3.4%, or 722, are pregnant at any given time. Again, out of Irvine’s 277,453 residents, about 722 are pregnant Asian women between 18 and 44. I will guess, not unreasonably, that anti-immigrant conservatives will have some difficulty in distinguishing Chinese and Chinese-American residents from the other Asian ethnic groups that call Irvine home.

The news stories on the recent arrests do not make clear how many of the mothers resided in Irvine. The OC Register says the birth tourism companies has as clients “thousands” of women, and OC Weekly has one LA-based company accused of serving 8,000 over 20 years. An earlier article says the 2015 raid which yielded the evidence for the arrests was of “three dozen” homes, and one wonders what the maximum throughput of clients could have been for that space. For the purposes of this post I will assume 400 clients of these services per year reside in Irvine. This is almost certainly a high estimate, since it comes from dividing Star Baby Care’s 8,000 total clients evenly across the 20 years that they were in business and assuming that they all lived (and continue to live at the same rate even post-raid) in Irvine. Nonetheless, it yields a workable figure of 100 clients in Irvine at any given time after dividing a year by the 3 months that clients apparently stay/stayed before giving birth and returning to China.

So, assuming that 100 Chinese mothers-to-be in Irvine are here after misrepresenting their intentions to customs agents, and 722 Asian mothers-to-be are just minding their own business, you have 87.8% odds of getting it wrong when accusing random Asian women of being a part of this criminal conspiracy. As it turns out, in a city where almost half of the population is Asian, it shouldn’t necessarily arouse suspicion to see pregnant Asian women in public.

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