Friday, July 13, 2018

Oster on breast feeding




Very nice and brief summary. Cleanliness is no joke, and breast feeding is known to be a lot cleaner and safer for infants than formula with contaminated water or in dirty bottles. But other benefits are far less clear.

Wednesday, July 11, 2018

Immigrants in the military

Several outlets including NPR were reporting last week about discharges of immigrants seeking to join the military, including the Army Times. It appears the development may have to do with the program for Military Accessions Vital to the National Interest (MAVNI), which emphasized recruiting for language skills especially in the Army, according to this Military.com article. A Vox.com article seems to identify security concerns stretching back to the Obama Administration combined with difficulty verifying backgrounds of immigrants from countries with less robust information systems.

Setting aside the impact on individuals for a moment, it is also useful to assess how big of a challenge this is for the military. The MAVNI document above, which appears to have been written in 2015, states that about 5,000 green card holders enlist each year, and that 109,250 have attained citizenship through military service since 9/11.

Active-duty force strength is about 1.34 million, according to Pew Research. It is harder to find the percent who are foreign born. In 2008, when forces were roughly the same size as they are today, there were about 65,000 immigrants on active duty, or about 5% of all active-duty forces, and more than two thirds had been naturalized. Ten years may have changed this somewhat, but these magnitudes imply something like 20,000 green card recipients or around 1.5% of forces.

Monday, July 9, 2018

Trade wars and recessions

A vox.com article by Matthew Yglesias references a great blog post by Paul Krugman guesstimating the outcome of a global trade war as a tariff hike of 40%, a reduction in imports of 70%, and an associated welfare cost of 2.1% of GDP.

Krugman is right that this isn't enormous, but I wanted to add this perspective:  If the labor share of GDP is 2/3, you would also end up with a 2.1% hit to GDP if you had roughly a 3% reduction in labor inputs. Since the financial crisis of late 2008, U.S. labor force participation has fallen about 3.2%, from 66.0% to about 62.8%.

I think that's revealing: it's consistent with the point that the world likely won't end as a result of a shock of this magnitude; and it's also useful to contextualize the shock this way, as something like the wave that swept a lot of people out of the labor force.

Breast feeding, parental leave, and child outcomes

The latest Administration kerfuffle on the international stage concerns the WHO and breast feeding. It's hard to know exactly what happened. An NPR interviewee describes the issue as having to do with deceptive marketing practices of formula companies; the BBC reports it was about striking language that promoted breast feeding, and inserting the phrase "evidence based."

What does the evidence suggest about breast feeding? I don't think it's as cut and dried as the BBC article pithily states: "years of research has found breast milk to be healthier than other substitutes." While we wait for somebody like Emily Oster to sift through the medical advice for us in her forthcoming book, here are some references I found helpful.

As you might imagine, there are few studies that are able to isolate the effects of breast feeding from family leave, which tends to increase breast feeding.


  • Baker and Milligan (JHE, 2008) examine changes in Canadian maternity leave and find relatively little evidence of any effects on children's well-being within the first 24 months.
  • Fletcher (Health Econ., 2011) looks at long-term educational outcomes and self-reported (retrospective!) breast feeding in the Add Health panel. He finds that differences in outcomes associated with breast feeding appeared to be driven by differences in parental behavior like treating siblings equally.


  • Colen and Ramey (Soc Sci Med, 2014) assess patterns in outcomes among children in the NLSY across a broad age range, 4 to 14, associated with breast feeding. They report that benefits were mostly associated with parental characteristics, which prompted their selection into breast feeding.


  • Lichtman-Sadot and Bell (JPAM, 2017) look at the introduction of paid family leave in California in 2004 and compare cohorts of children born before and after the policy change. They report large effects of paid family leave on 6 health metrics observed mostly via parental self-report at Kindergarten.


I would say there is some evidence that family leave can improve outcomes, but there is not much evidence to suggest that the primary channel is breast feeding.

Monday, July 2, 2018

Native employment rose with immigration

A colleague and I examined ACS data from 2005 to 2016 and found evidence that native employment actually rose along with U.S. immigration, contrary to what one might expect based on basic economic theory where labor demand isn't shifting.

Mao-Mei Liu and I applied a standard statistical model in social science, panel fixed effects, to public-use microdata areas (PUMAs) in the U.S. over the period covered by the American Community Survey (ACS). We were concerned that we'd find something that was irregular but only because of the Great Recession. One could easily imagine seeing that the recession dried up employment for immigrants and natives alike, and that would tell us little about how the two themselves were related.  But instead what we found was a remarkably robust result across time periods and Census divisions: native employment seemed to trend upward by a small amount with immigration.

I'm particular keen on the point estimate of the average effect, which showed something like 1 additional native employed for every 20 more immigrants in the local labor force.  This sounds a lot like a situation where foreign-born labor combines with native labor, where the native labor might specialize in communications. There could be many other ways in which labor combines, and we did not examine industries or occupations.

Friday, June 1, 2018

Marshmallows and wealth

Here’s a nifty Atlantic article about the famous Marshmallow Test of delayed gratification in childhood and later-life outcomes. As one might expect, family background matters a lot in determining whether you can wait on that marshmallow. An easy way to see why is to imagine why a child might be hungry for the marshmallow.

Thursday, August 31, 2017

Paternal age in the news

Yesterday the NY Times reported on rising paternal age in the U.S., which on average "has increased over the past 44 years from 27.4 to 30.9 years," according to a new study out of Stanford.

The Times article also cites a 2016 study in Nature Genetics that finds no evidence for the hypothesis that advanced paternal age causes schizophrenia and autism in offspring because of de novo mutation. My colleague Jennifer Roff and I wrote about a related set of results in 2010, where we found that family economics appeared to explain the negative correlation observed between paternal age and children's neurocognitive outcomes. The Nature Genetics study argues that older dads are genetically different; we argued that they are phenotypically different.