The Ambrosini Critique

I just counted the number of men and women grad students in the Berkeley Math department. Not being able to gender non-European names, I count 120 men and 25 women. That’s a 1 to 5 ratio.

According to the graph here, if IQs in that department are at or above 175 IQ (assuming IQ is a good proxy for math ability or at least the difference between the male and female distributions of math ability is similar to the difference in distribution of IQ), then variation in math ability can explain the underrepresentedness¹ of women in that department.

Well, according to the Berkeley math admissions page, applicants score above the 80th percentile in the math subject test. Assuming this test is only taken by math majors and that the average attendee is smarter than the average applicant, we can assume Berkeley math grad students are probably in the 90th percentile of math grad students (another way to get this percentile would be to assume all the top students go to Berkeley, its the top math program, and estimate the total number of math grad students… but I’m too lazy).

Ok. So, using the distribution of GRE scores on this page (pdf) and using this table to convert GRE to IQ, this means the average IQ at Berkeley Math is 146.92. Rounding to significant digits, this would suggest Berkeley students are 2 standard deviations too dumb to justify the gender imbalance.

Damn sexists… or there’s more problems with this exercise than I can name.

1. Get your prefix here! Suffix here! Get your hot, fresh -fixes! [↩]

People are saying Larry Summers is “vindicated” by a study showing males have higher variance in math ability than females. Does it make sense to talk of vindication for a scientist when data is found supporting his or her hypothesis?

According to Google:

Definitions of Vindicated on the Web:
* absolved: freed from any question of guilt; “is absolved from all blame”; “was now clear of the charge of cowardice”; “his official honor is …
wordnet.princeton.edu/perl/webwn

* “Vindicated” is a song by Dashboard Confessional released on the 2004 soundtrack for the movie Spider-Man 2. This track can be considered the theme for the Spider-Man 2 movie. The song is also featured on the Bonus Track edition of their 2006 album, Dusk and Summer.
en.wikipedia.org/wiki/Vindicated

* justified, avenged or cleared of blame
en.wiktionary.org/wiki/vindicated

Larry Summers isn’t a song and people aren’t saying his claims are vindicated (and they’re not because these data were more or less known at the time of the controversy) and Summers hasn’t been avenged. So why all the drama?

Larry Summers has only been vindicated if you’re playing the same game the Harvard faculty was when they had Summers fired, i.e. engaging in a War on Science.

So internet, stop saying this study vindicates him!

In any case the analogy [between money and communion wafers] doesn’t hold because money does not involve magical transformation through ritual, its value is an agreement, not a miracle.

— Righteous Bubba

Prof. Caplan thinks you should be able to answer questions like these correctly to be able to vote:

Which rights are guaranteed by the First Amendment?
How many Supreme Court justices are there?
What are the 13 original states?
Who has the power to declare war?

This is neat:

(h/t ct)

The restaurants==more calories assumption of the obesity paper by Gomis-Porqueras and Peralta-Alva I wrote about the other day is suspect given the findings of this paper:

But simple correlations between restaurants and overeating may conflate the impact of changes in supply and demand. People choose where and how much to eat. A key question is whether the growth in restaurant supply, in terms of both number of establishments and portion sizes, is contributing to the obesity epidemic, or whether it merely reflects changes in consumer preferences.

What’s driving the spurious correlation?

First, there is selection bias in who eats at restaurants; people who eat at restaurants also consume more calories when they eat at home. Second, when eating relatively large portions at restaurants, people tend to reduce other calorie consumption at other times during the day. After accounting for these factors, eating a meal at a restaurant is associated with only 24 additional calories.

Restaurants aren’t the cause of the obesity problem, but they’re targeted with expensive regulations:

Restricting a single source – restaurants – is therefore unlikely to affect obesity, as confirmed by our findings. This mechanism may also underlie the apparent failure of so many targeted obesity interventions (Kolata 2006). Despite their ineffectiveness, such policies have the potential to generate considerable deadweight loss. We measure the potential deadweight loss of policies targeted at restaurants and find it to be as high as $33 billion annually.

Because the Gomis-Porqueras/Peralta-Alva paper wasn’t about obesity per se, the Anderson/Matsa’s conclusions don’t really contradict it. People are going to restaurants more, but that’s not why they’re getting fatter.

Having been baptized into the DSGE faith, I’m compelled by solemn duty to uphold the tenets of the Prescottian Creed and defend macro from the heresies of the unbelievers in the Public and Labor offshoot of the Reduced Form sect. In other words, I have issues with the Anderson/Matsa paper.

The biggest issue I have is, like too many micro papers, their conclusions are much more broad than their findings. Their sample includes only a handful of States and because they use highway access as a way to measure access to restaurants (and there’s good reasons to do so), they limit their study to rural zip codes that lie within 10 miles of an interstate.

In this sub-sample, they found a positive relationship between distance to a highway and the distance to restaurants. They also found no correlation between BMI and distance from highways. Suggestive, ain’t it. They then claim to be shocked (SHOCKED!) to not have found any confounding variables that when considered might remove an underlying relationship between BMI and access to freeways. Thus, restaurants have nothing to do with obesity anywhere. QED.

I feel like there might be a missing step or two connecting their findings to their conclusion. Well, ok in their conclusion section of the paper they threw skeptics like me a bone: “Although our results apply specifically to rural consumers, the central conclusions are likely to generalize to urban consumers as well.” Given this is all they say about generalizability, its not much of a bone.

Also, they’re measuring distance from the home in this study, but where do people (or husbands or wives) work? In town, near the restaurant maybe? Maybe people that live far away from restaurants do have access to them after all.

Correctly, of course.

1) Suppose you had $100 in a savings account and the interest rate was 2% per year. After 5 years, how much do you think you would have in the account if you left the money to grow?
a) More than $102
b) Exactly $102
c) Less than $102
d) Do not know

2) Imagine that the interest rate on your savings account was 1% per year and inflation was 2% per year. After 1 year, would you be able to buy more than, exactly the same as, or less than today with the money in this account?
a) More than today
b) Exactly the same as today
c) Less than today
d) Do not know

3) Do you think that the following statement is true or false? “Buying a single company stock usually provides a safer return than a stock mutual fund.”
a) True
b) False
c) Do not know

Linky.

I don’t usually do this, but I thought this was a fun paper:

In this paper, we use dynamic general equilibrium theory to derive the quantitative implications of a decline in the relative monetary and time costs of food prepared away from home on the caloric intake by American households. Motivated by the empirical literature, we consider two channels that lower the relative costs of food prepared away from home. One is productivity improvements in the production of processed foods. The second is actual declines in income taxes and in the gender wage gap, which increases the opportunity cost of cooking at home from scratch. Households respond optimally to this decline in relative costs by consuming more food prepared away from home.

Why are Americans getting fatter? Because they’re eating out more and eating at restaurants leads to more intake of calories. Why are they eating out more? A little bit of it is the increasing availability of cheap restaurant food (like Micky D’s), but mostly its because of increasing opportunity costs. Income taxes have gone down making it more profitable to work outside the home so people don’t have time to cook. Also, gender wage disparities have decreased. Equalization of pay between the genders means women find working to be more profitable than making dinner for the family. Men aren’t picking up the slack; the lazy bastards do a whopping 11-15 minutes a day of food preparation in the home.

BTW, Americans have been basically sedentary since the 70’s so this can’t explain increasing obesity since then.

UPDATE: It just occurred to me that Megan didn’t bring up opportunity costs when discussing NYC’s effect on diet in her latest divalog. They talked about peer effects (which may be how agents find the dynamic equilibrium). I wonder why NYC is an exception to the story told in this paper. Maybe the high calorie/eating out connection is broken at high income levels. This makes sense because “good” restaurant food is probably a normal good. This would have a mitigating effect on the results of the paper.

The paper really shows a relationship between eating out and opportunity costs. The claims about obesity stand (and probably fall… at least a bit) on the assumption that eating out always means eating more calories.

Tim Lambert, responding to this opinion piece¹, says:

If the hot spot really is missing is does not prove that CO2 is not causing warming, but it would indicate something wrong with the models. (Which might mean that things are worse than what the models predict.)

That parenthetical kills me. Somebody should try it in a macro seminar. “No my model doesn’t show the characteristic hump shaped inflation response, but this means my model is wrong. The correct model might make my conclusion even stronger!”

But what really pisses me off about the piece is its title. Yeah, yeah, I know its a blog post, but its a blog post at “Scienceblogs” which I would expect to be more scientific-y or something. Anyway, how is a facts-driven, plausible sounding critical review a “war on science”?

In the backwoods where I’m from, facts-driven plausible sounding stories are science.

1. why in the deuce is science being argued in the opinion pages! [↩]

Check out this comment thread:

I have a master’s degree in computer science and an MBA on the accounting track, and I’m delivering pizzas. Maybe if I’d moved to India I would have a better chance at getting a job.

Also, there’s this great line: “The whole H-1B is a joke – a rape of the American tech professional!”.

For the thousands of engineers that develop on the platforms invented by foreign guest workers (e.g.) its not quite a rape. I suspect those folks wouldn’t get worked up enough to post vitriol (”Will Wilkinson is clueless, and has no data to base his delusional ideas on. According to this idiot…”) on a web page, though.