satt

Karma: 4,126

satt Oct 13, 2015, 11:55 PM
7 points
in reply to: philh’s comment on: Stupid questions thread, October 2015
Also also not an economist, although I took economics classes once.

I had a go at translating the simple model into one of those supply ‘n’ demand scribbles. For parsimony I assumed a straight line for the supply curve. For the demand curve I assumed no one bought more than the subsistence level of food, and that if the price was too high to reach that level, everyone simply bought as much food as they could with a constant budget.

That makes the status quo

and after a universal jump in income to relax everyone’s budget constraint, the non-vertical part of the demand curve rises:

At both times the intersection of S and D determines the equilibrium price. The intersection stays in the same place, so, in this incredibly simplified model, the equilibrium price is unaffected by everyone getting more money.

Being so primitive, this graphical model does not remotely prove that the price would stay the same in real life. But in trying to figure out why the graphical model disagreed with the verbal model, I managed to put my finger on why the two differ, and I think it’s a hole in the verbal model.

The verbal model observes that if people have $300/month, all of the retailers could jack the price of food up to $300/month, and everyone would be compelled to pay that. But that assumes coordination/cooperation/collusion between retailers rather than competition. If every food retailer raised their price to $300/month, any one of those retailers could swoop in and steal the others’ custom by cutting their own price to $299/month. And then another retailer could cut their price to $298/month, and so on. By the obvious inductive argument, the equilibrium price would wind up at the same $200/month it was before.

satt Oct 7, 2015, 4:15 AM
8 points
in reply to: moridinamael’s comment on: Deliberate Grad School
I mostly agree, but would add two caveats.

Relying too much on getting one very specific advisor is risky. Most advisors are middle-aged (or outright old), especially those with Nobel Prizes, and they do sometimes die or move away with little notice. If that happens, universities can be very bad about finding replacements (let alone comparably brilliant replacements) for any students cast adrift.

Also, an adviser’s personality & schedule are as important as their research skills: a Nobel Prize winner who’s usually away giving speeches, and is a raging, neglectful arsehole when they are around, is likely to be more of a hindrance than a help in getting a PhD. Put like that, what I just wrote is obvious, but I can imagine it being the kind of thing potential applicants would overlook.

satt Oct 7, 2015, 1:47 AM
2 points
on: Deliberate Grad School
Me previously on the topic of getting a PhD.

satt Sep 22, 2015, 4:23 AM
9 points
in reply to: James_Miller’s comment on: Open thread, Sep. 21 - Sep. 27, 2015
I made a grab for some low-hanging knowledge on the counterfactual question by looking at the first couple of pages of a Google Scholar search for articles I could access which offered background on the topic. (I don’t have the time or the interest to do anything like a real literature review, but I expect even a cursory Google Scholar search to be more reliable than a lone NewsBusters article.) Ignoring the books and paywalled Foreign Affairs articles I can’t read, I got
- Michael J. Mazarr’s 1995 “Going Just a Little Nuclear: Nonproliferation Lessons from North Korea” in International Security
- Larry A. Niksch’s 2005 Congressional report “North Korea’s Nuclear Weapons Program”
- Stephen M. Walt’s 2000 “Two Cheers for Clinton’s Foreign Policy” in Foreign Affairs (accessible only because Walt mirrors it on his Harvard website)
- Andrew Mack’s “A Nuclear North Korea: The Choices Are Narrowing” in the summer 1994 issue of World Policy Journal
- The 1999 “Review of United States Policy Toward North Korea: Findings and Recommendations”, by a “North Korea policy review team, led by Dr William J. Perry”
I haven’t perused these from start to finish, and even if I had I couldn’t discuss them comprehensively in a blog comment. So I have to give a radically compressed (hence necessarily selective) digest of the bits I saw which shed light on the counterfactual question.

First, Mazarr’s essay. It summarizes itself, but even the summary won’t fit here, so I skip to its p. 104, where Mazarr referred to NK’s “alleged one or two nuclear weapons” (fitting NBC’s report that NK had a nuclear weapon), and quote a longer block from the same page:

Down one road lies an ultimatum—a demand for perfect confidence and complete disarmament; its way-stations are confrontation, an end to IAEA inspections and other forms of international control [...] sanctions, and possibly war. The other road holds a more accommodating approach, lessened tensions, expanded international monitoring [...] and the hope of eventual disarmament; its price is a greater near- to medium-term risk that the proliferant might be able to hide a rudimentary nuclear program.

Mazarr adds that, in practice, the US “always resorts” to the softer approach “in cases of hard-core proliferation”, having “accepted ambiguous proliferation in India and Israel for many years”, and likewise didn’t pursue an all-out approach against India & Pakistan. Further along, on p. 110, in the section on sanctions:

Even had a tougher approach been more appealing, there was little chance it would have worked. North Korea had a long history of rejecting international opinion when phrased as a demand and accompanied by sanctions or the threat of them. Nor could economic sanctions have been effective without the participation of China, South Korea, Russia, and Japan, each of which expressed some degree of unease with a confrontational approach to the North, and reluctance to take any steps that might spark a rapid collapse of the North Korean system.

The section on sanctions was generally pessimistic, though Mazarr granted that “the de facto sanction of existing trade restrictions” could help shape “a proliferant’s motives” (p. 111), and that NK seemed to have an interest “in avoiding condemnation and sanctions as voted by the Security Council” (p. 112). Mazarr was even more doubtful that military action would “have offered a definitive answer to the North Korean nuclear challenge” because it could have “led directly to a Korean war” and “military strikes [...] probably would not work” anyway (p. 113).

Mazarr’s essay was most optimistic about the kind of approach represented by Clinton’s ’94 agreement: “a broad-based policy of incentives built around the offer of a package deal” (p. 114). Even a rejected package deal “would have its uses” because it “would force North Korea to make a clear choice, deprive it of excuses, and seize the political high ground, firming up a political consensus (including China) for UN sanctions” (p. 117).

Niksch’s report doesn’t seem useful for the counterfactual question at issue, because the report is mainly about the (second) Bush administration’s goals & actions. My skimming revealed a description of the US’s obligations under the ’94 Agreed Framework, but no substantial, explicit evaluation of alternatives to the Framework.

Walt’s article is a general assessment of Clinton’s foreign policy. From its paragraph about the 1994 NK deal, on pages 72-73:

Hard-liners have criticized Clinton for rewarding North Korea’s defiance of the nonproliferation regime, but they have yet to offer an alternate policy that would have achieved as much with as little. A preemptive air strike might well not eliminate North Korea’s nuclear capability. Moreover, both South Korea and Japan opposed the use of force. [...] the situation called for flexibility, persistence and creativity; the administration displayed them all. Without the 1994 Agreed Framework, North Korea would almost certainly have obtained enough fissile material for a sizable number of nuclear bombs. [...] Given the limited array of options and the potential for disaster, Clinton’s handling of North Korea is an impressive diplomatic achievement.

Mack’s essay reminds me of Mazarr’s in its scepticism about sanctions (e.g. p. 32: “What all this suggests is that imposing sanctions will be far more problematic than their more naive proponents in the West realize”), and Mack was at least as negative as Mazarr about military action, writing on p. 33 that “[t]he idea of resolving the nuclear issue by ‘taking out’ the Yongbyon nuclear facilities suffers from three fatal defects”. Those three, briefly: (1) “it is by definition impossible to hit unknown targets” potentially kept secret by a “paranoid” regime; (2) “‘surgical strikes’ against Yongbyon might not only fail to destroy all of the North’s nuclear program, they would also unleash a very unsurgical war against the South”; and (3) “it would be politically impossible to pursue the military option until the less risky alternatives of persuasion and sanctions had [...] failed. But sanctions would likely take years to have the desired effect”. Ultimately, Mack was not sure anything would work. From p. 35:

Given the very real possibility that neither persuasion nor bribery, economic coercion, military action, or even unilateral reassurance will divert Pyongyang from its nuclear path, the international community needs to start thinking about what this may mean for regional—and global—security.

The 1999 Perry et al. review reads to me as broadly positive about the Agreed Framework, asserting on p.2 that it

succeeded in verifiably freezing North Korean plutonium production at Yongbyon — it stopped plutonium production at that facility so that North Korea currently has at most a small amount of fissile material it may have secreted away from operations prior to 1994; without the Agreed Framework, North Korea could have produced enough additional plutonium by now for a significant number of nuclear weapons.

The review team behind the report recommended on p. 6 that the Agreed Framework “be preserved and implemented” as one recommendation of six:

With the Agreed Framework, the DPRK’s ability to produce plutonium at Yongbyon is verifiably frozen. Withou the Agreed Framework, however, it is estimated that the North could reprocess enough plutonium to produce a significant number of nuclear weapons per year. The Agreed Framework’s limitations, such as the fact that it does not verifiably freeze all nuclear weapons-related activities [...] are best addressed by supplementing rather than replacing the Agreed Framework.

Insofar as these sources are accurate and I’ve understood and digested them properly, it’s not only possible but likely that Clinton did about as well on this count as a different president could’ve. If so, then (even if NK didn’t already have a nuclear weapon in ’94) I’d think it unfair to assert that “Clinton let North Korea get nuclear weapons” as if there were an alternative decision Clinton could’ve taken to delay North Korea’s first nuclear test for 13+ years.

(2/2)
What links here?
- satt's comment on Open thread, Sep. 21 - Sep. 27, 2015 by MrMind (Sep 22, 2015, 4:23 AM; 5 points)

satt Sep 22, 2015, 4:23 AM
5 points
in reply to: James_Miller’s comment on: Open thread, Sep. 21 - Sep. 27, 2015
The linked article does an OK job of documenting that contemporary news reports were too optimistic about how much Clinton’s 1994 deal would constrain North Korea’s bomb seeking. However, I don’t think that’s an adequate basis for “Clinton let North Korea get nuclear weapons” — not least because the article itself echoes, in apparent agreement, NBC’s contemporary claim that NK already had a nuclear bomb.

Even setting aside that claim, I wouldn’t be confident in inferring that “Clinton let North Korea get nuclear weapons” merely because Clinton made a deal and 12 years later (and 6 years after Clinton left office) NK set off a nuke. Given my original state of ignorance (I didn’t know anything about this 1994 deal before this thread), I can’t rule out the possibilities that (1) Clinton actually made smart moves which were later vitiated by Bush or a lower-ranked politician, or that (2) Clinton made the best of a bad hand, there being no reasonable counterfactual where a US president in 1994 could’ve ensured, without triggering some patently worse consequence, that NK’s first nuclear explosion happened substantially after 2006.

(1/2)
What links here?
- satt's comment on Open thread, Sep. 21 - Sep. 27, 2015 by MrMind (Sep 22, 2015, 4:23 AM; 9 points)

satt Sep 19, 2015, 1:20 PM
7 points
in reply to: [deleted]’s comment on: Rationality Quotes Thread September 2015
I don’t see the rationality-relevant aspect of that quotation...

satt Sep 19, 2015, 12:33 PM
3 points
in reply to: gwern’s comment on: Open thread, Sep. 14 - Sep. 20, 2015
It does. However...

I see now I could’ve described the model better. In Stan I don’t think you can literally write the observed data as the sum of the signal and the noise; I think the data always has to be incorporated into the model as something sampled from a probability distribution, so you’d actually translate the simplest additive model into Stan-speak as something like
```
data {
    int<lower=1> N;
    int<lower=1> Ncities;
    int<lower=1> Nwidgets;
    int<lower=1> city[N];
    int<lower=1> widget[N];
    real<lower=0> sales[N];
}

parameters {
    real<lower=0> alpha;
    real beta[Ncities];
    real gamma[Nwidgets];
    real<lower=0> sigma;
}

model {
    // put code here to define explicit prior distributions for parameters
    for (n in 1:N) {
        // the tilde means the left side's sampled from the right side
        sales[n] ~ normal(alpha + beta[city[n]] + theta[widget[n]], sigma);
    }
}
```
which could give you a headache because a normal distribution puts nonzero probability density on negative sales values, so the sampler might occasionally try to give sales[n] a negative value. When this happens, Stan notices that’s inconsistent with sales[n]’s zero lower bound, and generates a warning message. (The quality of the sampling probably gets hurt too, I’d guess.)

And I don’t know a way to tell Stan, “ah, the normal error has to be non-negative”, since the error isn’t explicitly broken out into a separate term on which one can set bounds; the error’s folded into the procedure of sampling from a normal distribution.

The way to avoid this that clicks most with me is to bake the non-negativity into the model’s heart by sampling sales[n] from a distribution with non-negative support:
```
for (n in 1:N) {
    sales[n] ~ lognormal(log(alpha * beta[city[n]] * theta[widget[n]]), sigma);
}
```
Of course, bearing in mind the last time I indulged my lognormal fetish, this is likely to have trouble too, for the different reason that a lognormal excludes the possibility of exactly zero sales, and you’d want to either zero-inflate the model or add a fixed nonzero offset to sales before putting the data into Stan. But a lognormal does eliminate the problem of sampling negative values for sales[n], and aligns nicely with multiplicative city & widget effects.

satt Sep 16, 2015, 1:17 AM
4 points
in reply to: philh’s comment on: Open thread, Sep. 14 - Sep. 20, 2015
Even if you know only the generating process and not an estimation procedure, you might be able to get away with just feeding a parametrization of the generating process into an MCMC sampler, and seeing whether the sampler converges on sensible posterior distributions for the parameters.

I like Stan for this; you write a file telling Stan the data’s structure, the parameters of the generating process, and how the generating process produced the data, and Stan turns it into an MCMC sampling program you can run.

If the model isn’t fully identified you can get problems like the sampler bouncing around the parameter space indefinitely without ever converging on a decent posterior. This could be a problem here; to illustrate, suppose I write out my version of skeptical_lurker’s formulation of the model in the obvious naive way —

sales(city, widget) = α × β(city) × γ(widget) + noise(city, widget)

— where brackets capture city & widget-type indices, I have a β for every city and a γ for every widget type, and I assume there’s no odd correlations between the different parameters.

This version of the model won’t have a single optimal solution! If the model finds a promising set of parameter values, it can always produce another equally good set of parameter values by halving all of the β values and doubling all of the γ values; or by halving α and the γ values while quadrupling the β values; or by...you get the idea. A sampler might end up pulling a Flying Dutchman, swooping back and forth along a hyper-hyperbola in parameter space.

I think this sort of under-identification isn’t necessarily a killer in Stan if your parameter priors are unimodal and not too diffuse, because the priors end up as a lodestar for the sampler, but I’m not an expert. To be safe, I could avoid the issue by picking a specific city and a specific widget as a reference widget type, with the other cities’ β and other widgets’ γ effectively defined as proportional to those:

if city == 1 and widget == 1: sales(city, widget) = α + noise(city, widget)

else, if city == 1: sales(city, widget) = α × γ(widget) + noise(city, widget)

else, if widget == 1: sales(city, widget) = α × β(city) + noise(city, widget)

else: sales(city, widget) = α × β(city) × γ(widget) + noise(city, widget)

Then run the sampler and back out estimates of the overall city-level sales fractions from the parameter estimates (1 / (1+sum(β)), β(2) / (1+sum(β)), β(3) / (1+sum(β)), etc.).

And I’d probably make the noise term multiplicative and non-negative, instead of additive, to prevent the sampler from landing on a negative sales figure, which is presumably nonsensical in this context.

Apologies if I’m rambling at you about something you already know about, or if I’ve focused so much on one specific version of the toy example that this is basically useless. Hopefully this is of some interest...

satt Sep 13, 2015, 8:54 PM
1 point
in reply to: Bound_up’s comment on: Open thread 7th september − 13th september

Where to find free online textbooks? [...]

And I’ve heard there are online sources of great books (EY once joked that everything worth reading was online); where can I find those?

I don’t know how up to date these suggestions are, but maybe they’re still useful.

satt Sep 13, 2015, 12:43 PM
0 points
in reply to: TheAncientGeek’s comment on: Why Don’t Rationalists Win?
Upvoted, but I want to throw in the caveat that some baseline level of epistemic rationalism is very useful for winning. Schizophrenics tend to have a harder time of things than non-schizophrenics.

satt Sep 13, 2015, 12:24 PM
2 points
in reply to: Vaniver’s comment on: Why Don’t Rationalists Win?
Previously.

satt Sep 10, 2015, 2:05 AM
0 points
in reply to: roland’s comment on: Open thread 7th september − 13th september

I did a quick search on LW but didn’t find any important article about information diet. Did I miss something?

I found a post that might be talking about the capital-I capital-D Information Diet you might be talking about.

There’ve been some other threads and a post about cutting down on news or eliminating news from one’s life, too.

Should we eliminate all news sources like some advocate?

It’s actually very plausible to me that a little news is the optimal amount for most people to deliberately consume, but I do mean a little — maybe 5 minutes a day as an order-of-magnitude guess — and one is probably not going to miss out on that much by cutting down to literally zero (though in a given time & place it might be a bad idea).

I’m aiming for the soft spot of eliminating all the unnecessary news while still getting those pieces that are relevant for me.

The first idea which pops into my mind is specialization: pick news/commentary sources where a specialist talks about a narrow topic they know well. In your tax code example, you might be able to find some interesting tax bloggers(!) who’d be likely to mention important changes to the tax code in your jurisdiction.

satt Sep 9, 2015, 10:38 PM
0 points
in reply to: gwern’s comment on: 2014 Survey Results

As I understand it, tests of normality are not all that useful because: they are underpowered & won’t reject normality at the small samples where you need to know about non-normality because it’ll badly affect your conclusions; and at larger samples [...], because real-world data is rarely exactly normal, they will always reject normality even when it makes not the slightest difference to your results

I agree that normality tests are too insensitive for most small samples, and too sensitive for pretty much any big sample, but I’d presumed there was a sweet spot (when the sample size is a few hundred) where normality tests have decent sensitivity without giving everything a negligible p-value, and that the LW survey is near that sweet spot. If I’d been lazy and used R’s out-of-the-box normality test (Shapiro-Wilk) instead of following goocy’s recommendation (Lilliefors, which R hides in its nortest library) I’d have got an insignificant p of 0.11, so the sample [edit: of non-zero donations] evidently isn’t large enough to guarantee rejection by normality tests in general.

Also, you don’t have to look at only one year’s data; you can look at 3 or 4 by making sure to filter out responses based whether they report answering a previous survey.

Certainly. It might be interesting to investigate whether the log-normal-with-zeroes distribution holds up in earlier years, and if so, whether the distribution’s parameters drift over time. Still, goocy’s complaint was about 2014′s data, so I stuck with that.

satt Sep 9, 2015, 2:08 AM
5 points
in reply to: DTX’s comment on: 2014 Survey Results
Thanks for prompting me to take a closer look at this.

The distribution is certainly very positively skewed, but for that reason that histogram is a blunt diagnostic. Almost all of the probability mass is lumped into the first bar, so it’s impossible to see how the probability distribution looks for small donations. There could be a power law there, but it’s not obvious that the distribution isn’t just log-normal with enough dispersion to produce lots of small values.

Looking at the actual numbers from the survey data file, I see it’s impossible for the distribution to be strictly log-normal or a power law, because neither distribution includes zero in its support, while zero is actually the most common donation reported.

I can of course still ask which distribution best fits the rest of the donation data. A quick & dirty way to eyeball this is to take logs of the non-zero donations and plot their distribution. If the non-zero donations are log-normal, I’ll see a bell curve; if the non-zero donations are Pareto, I’ll see a monotonically downward curve. I plot the kernel density estimate (instead of a histogram ’cause binning throws away information) and I see

which is definitely closer to a bell curve. So the donations seem closer to a lognormal distribution than a Pareto distribution. Still, the log-donation distribution probably isn’t exactly normal (looks a bit too much like a cone to me). Let’s slap a normal distribution on top and see how that looks. Looks like the mean is about 6 and the standard deviation about 2?

Wow, that’s a far closer match than it has any right to be! Admittedly, if I ask R to run a Lilliefors test, the test rejects the hypothesis of normality (p = 0.0007), and it remains the case that the donations are neither log-normal nor power-law distributed because some of the values are zero. But the non-zero donations look impressively close to a log-normal distribution, and I really doubt a Pareto distribution would fit them better. (And in general it’s easy to see Pareto distributions where they don’t really exist.)
What links here?
- satt's comment on Open thread, Sep. 14 - Sep. 20, 2015 by MrMind (Sep 19, 2015, 12:33 PM; 3 points)

satt Sep 2, 2015, 1:48 AM
2 points
in reply to: Vaniver’s comment on: Open Thread August 31 - September 6
And Adams himself says the “smart money” is on Silver’s prediction! I think Adams’s prediction is more performative than prognostic, even allowing for ordinary unconsciously bad calibration.

satt Sep 1, 2015, 1:45 AM
2 points
in reply to: entirelyuseless’s comment on: Rationality Quotes Thread August 2015
I arrive late but with a link to the Kaj_Sotala post you’re probably thinking of:

I sent two messages to Eugine, requesting an explanation. I received a response today. Eugine admitted his guilt, expressing the opinion that LW’s karma system was failing to carry out its purpose of keeping out weak material and that he was engaged in a “weeding” of users who he did not think displayed sufficient rationality.

satt Sep 1, 2015, 1:35 AM
0 points
in reply to: [deleted]’s comment on: Rationality Quotes Thread August 2015

But again: now you are equating irrationality with deliberate suicide.

Whether PradyumnGanesh is or isn’t (though I don’t think they are), that doesn’t change their observation that self-inflicted violence is a relatively common form of violence, at least going by fatal violence.

satt Sep 1, 2015, 12:00 AM
7 points
in reply to: James_Miller’s comment on: Open Thread August 31 - September 6
Forgetting what I know (or think I know) about Scott Adams, Donald Trump, Nate Silver, Jeb Bush, whoever, and going straight to the generic reference class forecast — I’m very sceptical someone could predict US presidential elections with 98% accuracy 14 months in advance.

satt Aug 31, 2015, 1:10 PM
0 points
in reply to: CCC’s comment on: Self-Congratulatory Rationalism
Your diagnosis sounds all too likely. I’d hoped to minimize the risk of this kind of thing by concretizing and focusing on a specific, publicly-observable example, but that might not have helped.

satt Aug 29, 2015, 12:06 PM
2 points
in reply to: CCC’s comment on: Self-Congratulatory Rationalism

Then “cogent” was probably the wrong word to use.

TheAncientGeek assented to that choice of word, so I stuck with it. His conception of the POC might well be different from yours and everyone else’s (which is a reason I’m trying to pin down precisely what TheAncientGeek means).

Okay, I appear to have been using a different definition (see definition two).

Fair enough, I was checking different dictionaries (and I’ve hitherto never noticed other people using “cogent” for “pertinent”).

Then you may very well be effectively applying the principle already. Looking at your reply to RomeoStevens supports this assertion.

Maybe, though I’m confused here by TheAncientGeek saying in one breath that I applied the POC to RomeoStevens, but then agreeing (“Thats exactly what I mean.”) in the next breath with a definition of the POC that implies I didn’t apply the POC to RomeoStevens.