Two views of Excel

Part of the Reinhart-Rogoff fall-out (see here for Joseph's take) has been a discussion of the role of Excel and similar programs in analytic work. Andrew Gelman has a post up on the subject that includes this quote from an unnamed statistics professor:

It’s somewhat surprising to see Very Serious Researchers (apologies to Paul Krugman) using Excel. Some years ago, I was consulting on a trademark infringement case and was trying (unsuccessfully) to replicate another expert’s regression analysis. It wasn’t until I had the brainstorm to use Excel that I was able to reproduce his results – it may be better now, but at the time, Excel could propagate round-off error and catastrophically cancel like no other software!

Followed by this assessment by Gelman himself:

Microsoft has lots of top researchers so it’s hard for me to understand how Excel can remain so crappy. I mean, sure, I understand in some general way that they have a large user base, it’s hard to maintain backward compatibility, there’s feature creep, and, besides all that, lots of people have different preferences in data analysis than I do. But still, it’s such a joke. Word has problems too, but I can see how these problems arise from its desirable features. The disaster that is Excel seems like more of a mystery.

In contrast, here's James Kwak discussing Excel (prompted by news that an embarrassingly simple spreadsheet error contributed to the London Whale fiasco and, yes, the similarities have been noted):

Microsoft Excel is one of the greatest, most powerful, most important software applications of all time.** [** But, like many other Microsoft products, it was not particularly innovative: it was a rip-off of Lotus 1-2-3, which was a major improvement on VisiCalc.] Many in the industry will no doubt object. But it provides enormous capacity to do quantitative analysis, letting you do anything from statistical analyses of databases with hundreds of thousands of records to complex estimation tools with user-friendly front ends. And unlike traditional statistical programs, it provides an intuitive interface that lets you see what happens to the data as you manipulate them.

As a consequence, Excel is everywhere you look in the business world—especially in areas where people are adding up numbers a lot, like marketing, business development, sales, and, yes, finance. For all the talk about end-to-end financial suites like SAP, Oracle, and Peoplesoft, at the end of the day people do financial analysis by extracting data from those back-end systems and shoving it around in Excel spreadsheets. I have seen internal accountants calculate revenue from deals in Excel. I have a probably untestable hypothesis that, were you to come up with some measure of units of software output, Excel would be the most-used program in the business world.

But while Excel the program is reasonably robust, the spreadsheets that people create with Excel are incredibly fragile. There is no way to trace where your data come from, there’s no audit trail (so you can overtype numbers and not know it), and there’s no easy way to test spreadsheets, for starters. The biggest problem is that anyone can create Excel spreadsheets—badly. Because it’s so easy to use, the creation of even important spreadsheets is not restricted to people who understand programming and do it in a methodical, well-documented way.*** [*** PowerPoint has an oft-noted, parallel problem: It’s so easy to use that people with no sense of narrative, visual design, or proportion are out there creating presentations and inflicting them on all of us. ]

To the extent there's a conflict here, I'm with Kwak on this one. For all their problems, I'm still a big fan of Excel and similar programs (such as the OpenOffice version I have on my laptop). They are indispensable in business for just the reasons Kwak lists.

Furthermore, I'd like to see them have a similar role in secondary and even primary education. I've long found spreadsheets to be a great tool for introducing basic concepts about math, computing and data visualization. You can see some sample lessons over at You Do the Math (one on functions and iteration, another on geometry and Monte Carlo techniques).

Swords and Wizardry Appreciation Day: Wow

I was amazed by the number and quality of Google+ responses to the Swords and Wizardry Appreciation Day.  It is pretty amazing the actual depth that this segment of the OSR actually has. 

One thing that really stood out is how easy it is to houserule S&W.  It is not just that they have the rules available in editable text format but that the rules themselves are very robust to tinkering.  This was one feature of more modern RPGs that I found difficult -- if you changed the assumptions of the game designers then the system showed problems.

The classic example is magic items in a D&D 3.X/Pathfinder world.  It is well known that the system presumes a certain level of magical gear for the players.  It also assumes that it is easy to make magical items.  Without these features, characters may well not operate as expected (the Monk 1/Druid X is much more formidable, for example). 

But with S&W, the alteration of a single rule rarely has repercussions across the system.  Sure, you can break it if you try to.  But the game plays well with many tweaks -- some of which are actually discussed in the rulebook (ideas like giving +1 to hit to two weapon fighters, or no memorized  wizard spells above level 6 but rituals instead).   This allows for a lot of freedom for groups to tinker and try to find the optimal balance. 

Swords and Wizardry Appreciation day

I was always surprised to be a Swords and Wizardry fan.  In a lot of ways I was a bigger fan of the original basic and expert (B/X) D&D books released after the first run of Dungeons and Dragons (and contemporaneous with Advanced Dungeons and Dragons). 

But the adventures sucked me in: both Grimmsgate and MCMLXII caught the sense of wonder of the early adventures and the lack of systematic approaches to everything that came latter.  Modern descendants of the original D&D (both the Wizards of the Coast and Paizo versions, both high quality products) lacked the sense of wonder that can from not fully understanding the world.  When everyone knows what an Ogre is and can do then there are few surprises left. 

The latest addition, in terms of rules, is Swords and Wizardry complete, which manages to have all of the key elements of the rules in 131 pages or so.  Sure some of the elements are not described in great detail (especially the spells) but that is a virtue.  I do think it was a mistake to include the spells above levels 5 or 6 . . . but the designer even admits to this in a sidebar.

Overall it was a refreshing vision of the game in an earlier era and one that I quite liked.  It was well timed to come out with the re-release of TSR D&D (both as premium reprints and as PDF files).  I have quibbles (no elf Druid despite an illustration to the contrary) but I think the vision and the production quality make up for these issues.  It is true that the system will work best for those who already understand D&D, but that really was how the hobby came to be (with the rule books often being somewhat inscrutable). 

Overall, I have really enjoyed this game system and I hope that Frog God Games continues to do high quality products like these ones (especially the modules). 

Tonight only -- free teleseminar on getting rich by writing for television

OK, not really, but a friend sent me this and I thought I'd pass it on because:

1. It sounded interesting;

2. It ties in (albeit weakly) with some recent discussions of distance learning;

3. Ken Levine (MASH, Cheers, Frasier) is one of the best bloggers on the subject of television and the business of writing.

Sorry about the late notice.

Tonight at 9 PM Eastern/ 6 PM Pacific I’ll be holding another FREE teleseminar. The topic is writing partners and my partner, David Isaacs will be joining me. We’ll answer all your questions. If you’re interested in participating and not already on the alert list here’s where you go to sign up. You must sign up by noon PDT. Did I mention it's FREE?

From unsupported hypothesis to conventional wisdom

I don't want to pick on Andrew Delblanco, who turned in an unusually well-balanced piece on MOOCs in a recent issue of the New Republic, but this passage bothered me quite a bit:

But the most persuasive account of the relentless rise in cost was made nearly 50 years ago by the economist William Baumol and his student William Bowen, who later became president of Princeton. A few months ago, Bowen delivered two lectures in which he revisited his theory of the “cost disease.” “In labor-intensive industries,” he explained, “such as the performing arts and education, there is less opportunity than in other sectors to increase productivity by, for example, substituting capital for labor.” Technological advances have allowed the auto industry, for instance, to produce more cars while using fewer workers. Professors, meanwhile, still do things more or less as they have for centuries: talking to, questioning, and evaluating students (ideally in relatively small groups). As the Ohio University economist Richard Vedder likes to joke, “With the possible exception of prostitution . . . teaching is the only profession that has had no productivity advance in the 2,400 years since Socrates.”

(for more along similar lines)

I'm not an economist, I haven't gone through Baumol and Bowen's research, and my college teaching experience is more than a decade out of date, so I'm certainly missing some salient points here, but if the hypothesis is true, I'd expect to see the following:

1. There should be a shortage of teachers

2. The percentage increase in wages for teaching should be greater than the percentage increase in overall tuition.

3. The share of tuition going to instructional costs should increase substantially relative to costs such as administration.

Rather than seeing all of these, it's not immediately obvious that we're seeing any. College teaching jobs are not easy to get, non-instructional costs seem to be more than holding their own and if you look at people who are paid solely to teach, their wages are increasing more slowly than tuition.

We have to be careful about treating informal observations as data, but with that caveat in mind, there are lots of reasons to question and not much evidence to support the hypothesis that a lack of technology-driven productivity gains by instructors are causing the sharp growth in tuition. Nonetheless, the idea has gone from interesting but unlikely theory to generally accepted fact.

Here's where I blame it all on Steven Levitt.

OK, not really, but this is an example of a journalistic fad that owes a lot to Freakonomics: propping up an argument with a semi-relevant economic allusion. This isn't the same as analyzing a problem using economic concepts (for example, trying to explain health care inflation as a principal agent problem). Instead, what we have here is the idea that explaining the concept is the same as arguing that it applies.

It is, of course, possible that cost disease really is driving the growth of tuition. This is an enormously complicated problem and complicated problems often look very different when examined in detail. Viewed from a distance, though, the idea that a lack of instructional productivity gains are driving the growth simply doesn't jibe with what we're seeing.

Lesson for Epidemiology

I am amazed that Mark was not all over this statistical modeling issue.  Matthew Yglesias posts the response from the authors here. 

A couple of quick thoughts.  First, no matter what you think of the authors of the original paper, I am inclined to applaud them for sharing both the source data and the statistical code used to analyze it.  It opened to them a comprehensive methodological critique but that could not have happened if they had not shared the source data and code.  The next result, from a scientific point of view, is a huge win (and I think this outweighs any actual errors, presuming that they were not intentional). 

Second, the whole issue of association versus causality is one that we should think more about.  It can be easy to slip in the fallacy of equivocation: asserting associational thinking when a study is attacked but interpreting it in a very causal manner in a policy discussion.  We have this problem all of the time.  We state associations like "people who eat red meat have a higher rate of disease" but then turn that into a recommendation of "eat less red meat". 

Now clearly one has to make an actual decision at some point and, in a lot of cases, the guidance can cause no harm.  But there are complex cases where this could matter a lot.  Consider the inverse association between smoking and Parkinson's disease.  Imagine (based on no data -- just a though experiment) that we extended this association to show slower progression in patients who continued to smoke.  That might make one think that cigarette smoking might be recommended to Parkinson's disease patients.  But if we are wrong (and the association is confounded or acting as a marker for some other trait) we will increase the rates of lung cancer and serious heart disease for no therapeutic benefit. 

Sometimes a randomized trial is an option.  But when it is not (as many exposures, like height or air quality, are hard to randomize) then there is a very delicate decision-making process.  It is very instructive and important to watch how other fields of study deal with these types of issues. 

Edit: It seems everyone has been looking at this question.  Some additional very good takes (over and above the Mark Thoma, Matt Yglesias and Mike Konczal linked above) include:

Andrew Gelman
Noah Smith
Paul Krugman
Tyler Cowen
Jonathan Chait

I continue to hope Mark Palko can be convinced to weigh in as well. 

Simply amazing tale of corporate governence

This was just amazing:

At Iris International, a medical diagnostics company based in Chatsworth, Calif., shareholders rejected all nine directors in May 2011. In keeping with the company’s policy, they submitted their resignations. And then they voted not to accept them. The nine stayed on the board. (The company was acquired in late 2012 by the Danaher Corporation.)

Assuming that this is a factually correct version of events and does not omit a key detail of some kind (always a risk when a story seems this outrageous), this is a remarkable separation of the owners of the company from their own board of directors.  In theory, could any board-member be replaced under these circumstances?  

A defense of the envelope method

Emily Oster has a provocative piece in Slate arguing against the envelope method of budgeting.  The crux of the argument appears to be:

The principle in question here is that “money is fungible.” In reality, all dollars are the same. There is no such thing as a gas dollar, a grocery dollar, a “fun” dollar. The Ramseys of the world argue you should just apportion them into the envelopes depending on what you think you might spend. But doing it this way is not actually the best way to dole out your money; you are not optimizing. Your money is just not working as hard as it should.

The system works great, as long as nothing ever changes. But the minute that some price changes, you’re in trouble. Here’s an extreme example. Imagine you drive to work, and your “gas money” envelope contains enough money to get you to work for the month, and maybe a little cushion. But then gas gets more expensive. You may first react by switching to a worse grade—say, from premium to regular (research shows many people do this). But if gas prices go up even more you simply will run out of money in the gas envelope. And then you won’t be able to get to work. Strictly following the envelope system here would be much, much worse than “cheating”: It’s certainly bad for your household budget if you miss work.

This presumes that the envelope system is static and the allocation of money in the envelopes never changes as prices change.  In other words that you do your budget once and never alter it.  It is clear that the strong form of this argument is actually a straw man -- would anybody let themselves be evicted because their rent went up but they could not bear to alter the values on the envelopes?  In general, this system will fail int he face of massive price and income volatility, but then nothing works well when you cannot plan for future income and expenses.

In my experience, the actual reason for the envelope system is one of two cases:

1. It reduces the complexity of managing a detailed household budget
2. You are really so poor that you have no ability to reallocate money

In my youth, I knew a lot of poor people (less so now, which is not necessarily a change for the better) and, in fact, was very poor for a time.  When your budget is tight enough it may really be the case that you cannot overspend on gas for the car without being unable to pay rent and/or eat and/or pay the electric bill.  People at this level of poverty do not necessarily have credit cards..

One of the features of being middle class is having flexibility.  Consider the plane ticket example that Dr. Oster presents: that makes total sense if you could (in theory) allow a credit card to increase.  But if the cost of the item would bring your bank account below zero and you don't have credit (or it has ruinous terms, like a payday loan or a 30% credit card) then you simply can't spend the money at all.

In practice this lack of flexibility can be very tough.  There are a lot of items that, bought in bulk, are cheap.  But bulk items are hard to transport on the bus (especially if it is crowded) and cost more (and you often cannot borrow against the future).  There are a surprising number of costs to being very poor (as opposed to being very frugal).

So, yes, it is possible for the envelope system to be too inflexible and that is not ideal.  But it is very, very useful when you have $110 after rent and utilities to make the rest of the month work.

Risk Aversion

What is the average interest rate these days?  According to one source it is puny:

Throughout the entire industry, however, the national average bank interest rate for savings accounts is only .21 percent

So why might be it rational to overpay your taxes by a small amount?  Consider this comment from Megan McArdle:

A tax refund is not free money you get from the government. It’s free money you gave to the government—by overpaying your taxes all year. You think the interest rate on your savings account is paltry? At least it's not zero, which is the amount Uncle Sam pays you for your yearlong interest free loan. (If you underpay the government, on the other hand, they charge you not only interest, but also penalties.)

On one hand her advice is completely sensible.  It makes a lot of sense to reduce a very large tax refund.  On the other hand, you need to save a lot of money for the 0.21% interest in that savings account to outweigh the interest and penalties.  Since even interest is 3% (15 times the savings rate), I think it makes sense to aim for a small refund rather than to make errors on both sides of the distribution (since underpaying is much more expensive than the lost revenue from overpaying).  This logic may not hold if interest rates and/or inflation pick up in the future. 

Did Dickens meet Dostoevsky? -- Opinions differ

Ross MacDonald books often start with a family that seems perfect except for one element out of place (like an angry, disturbed child) but when the hero starts to tug on that one thread the entire illusion falls apart.

University of California Berkeley Prof. Eric Naiman has come close to the scholarly equivalent of a Ross MacDonald novel in his recent essay in the Times literary supplement (via LGM). He finds one thread out of place, in this case an unlikely meeting between two famous novelists.By tugging on that thread Naiman uncovers a hoax of truly incredible scale and complexity. (Literally incredible at first. I Googled a half dozen of Naiman's facts before I decided he wasn't the one playing games.)

You really need to read the whole thing for yourself but one section near the beginning was particularly relevant to some of our recent discussions.

Late in 2011, Michiko Kakutani opened her New York Times review of Claire Tomalin’s biography of Charles Dickens with “a remarkable account” she had found in its pages. In London for a few days in 1862, Fyodor Dostoevsky had dropped in on Dickens’s editorial offices and found the writer in an expansive mood. In a letter written by Dostoevsky to an old friend sixteen years later, the writer of so many great confession scenes depicted Dickens baring his creative soul:

“All the good simple people in his novels, Little Nell, even the holy simpletons like Barnaby Rudge, are what he wanted to have been, and his villains were what he was (or rather, what he found in himself), his cruelty, his attacks of causeless enmity toward those who were helpless and looked to him for comfort, his shrinking from those whom he ought to love, being used up in what he wrote. There were two people in him, he told me: one who feels as he ought to feel and one who feels the opposite. From the one who feels the opposite I make my evil characters, from the one who feels as a man ought to feel I try to live my life. ‘Only two people?’ I asked.”

I have been teaching courses on Dostoevsky for over two decades, but I had never come across any mention of this encounter. Although Dostoevsky is known to have visited London for a week in 1862, neither his published letters nor any of the numerous biographies contain any hint of such a meeting. Dostoevsky would have been a virtual unknown to Dickens. It isn’t clear why Dickens would have opened up to his Russian colleague in this manner, and even if he had wanted to, in what language would the two men have conversed? (It could only have been French, which should lead one to wonder about the eloquence of a remembered remark filtered through two foreign tongues.) Moreover, Dostoevsky was a prickly, often rude interlocutor. He and Turgenev hated each other. He never even met Tolstoy. Would he have sought Dickens out? Would he then have been silent about the encounter for so many years, when it would have provided such wonderful fodder for his polemical journalism?

Several American professors of Russian literature wrote to the New York Times in protest, and eventually a half-hearted online retraction was made, informing readers that the authenticity of the encounter had been called into question, but in the meantime a second review of Tomalin’s biography had appeared in the Times, citing the same passage. Now it was the novelist David Gates gushing that he would trade a pile of Dickens biographies for footage of that tête-à-tête. While agreeing with Tomalin’s characterization of this quotation as “Dickens’s most profound statement about his inner life”, he found its content less astonishing than she: “it’s only amazing because it’s the image-conscious Dickens himself coming out and saying what anybody familiar with his work and his life has always intuited”.

Shortly thereafter, the Times website appended to the online version of Gates’s review the same cautionary note that had already been attached to Kakutani’s. But on January 15, 2012, the paper’s “Sunday Observer” section published yet a third article on Dickens that quoted from Dostoevsky’s letter. (The same online disclaimer was soon appended to this piece as well.) The newspaper’s collective unconscious was unable to give the story up. It demands retelling, and by now Dickens and Dostoevsky can be found meeting all over the web. Their conversation appeals to our fancy while, as Gates realized, comforting us with a reaffirmation of what we already know. Moreover, this reassuring familiarity applies not only to Dickens, but also to Dostoevsky. The man who asks “Only two?” is a writer who already knows what Mikhail Bakhtin would eventually write about him, who is presciently aware of his late-twentieth-century canonization as the inventor of literary polyphony.

I wondered if Naiman was being overly harsh when he called the retraction 'half-hearted.' He wasn't:

Correction: October 29, 2011 

The Books of The Times review on Tuesday, about “Becoming Dickens: The Invention of a Novelist” by Robert Douglas-Fairhurst, and “Charles Dickens” by Claire Tomalin, recounted an anecdote in Ms. Tomalin’s book in which Dostoyevsky told of meeting Dickens. While others have also written of such a meeting and of a letter in which Dostoyevsky was said to have described it, some scholars have questioned the authenticity of the letter and whether the meeting ever occurred.

I know I've been harping on this but there's a big and important issue with modern journalism's indifference to getting the facts right. The difficulty involved in checking a story has decreased by orders of magnitude and yet, even at our best papers, Twenty-first Century reporting is often less accurate than Twentieth Century work. Part of the problem is he belief that you're in the clear when you publish something that obviously wrong if you later add a weaselly some-people-disagree disclaimer at the bottom.

But enough scolding. Go read the Naiman piece. You will not find anything else like it.

Coding boot camp

Interesting story both from an educational and labor-economics standpoint. More to come on this one.

From the AP:

Instead, he quit his job and spent his savings to enroll at Dev Bootcamp, a new San Francisco school that teaches students how to write software in nine weeks. The $11,000 gamble paid off: A week after he finished the program last summer, he landed an engineering job that paid more than twice his previous salary.   

“It’s the best decision I’ve made in my life,” said Shimizu, 24, who worked in marketing and public relations after graduating from the University of California, Berkeley in 2010. “I was really worried about getting a job, and it just happened like that.” Dev Bootcamp, which calls itself an “apprenticeship on steroids,” is one of a new breed of computer-programming school that’s proliferating in San Francisco and other U.S. tech hubs. These “hacker boot camps” promise to teach students how to write code in two or three months and help them get hired as web developers, with starting salaries between $80,000 and $100,000, often within days or weeks of graduation.

“We’re focused on extreme employability,” said Shereef Bishay, who co-founded Dev Bootcamp 15 months ago. “Every single skill you learn here you’ll apply on your first day on the job.”

These intensive training programs are not cheap — charging $10,000 to $15,000 for programs running nine to 12 weeks — and they’re highly selective, typically only admitting 10 to 20 percent of applicants. And they’re called boot camps for a reason. Students can expect to work 80 to 100 hours a week, mostly writing code in teams under the guidance of experienced software developers. “It’s quite grueling. They push you very hard,” said Eno Compton, 31, who finished Dev Bootcamp in late March. Compton is finishing his doctorate in Japanese literature at Princeton University, but decided he wants to be a software engineer instead of a professor.

Weekend blogging -- Geoffrey Lewis

It's always cool to discover unexpected talents in familiar figures, like the actor you've seen playing a hundred "blank-faced hicks" who turns out to know more about dialect than perhaps anyone in Hollywood.

Along similar lines, I'd always liked Geoffrey Lewis's amiable sidekicks, but it turns out he was just as well known in acting circles as an Oscar nominated monologuist.

The even more indefensible Michelle Rhee

USA Today's Greg Toppo drives what should be the final nail into the coffin of Michelle Rhee's reputation (via Esquire's Charles Pierce):

District of Columbia Public Schools officials have long maintained that a 2011 test-cheating scandal that generated two government probes was limited to one elementary school. But a newly uncovered confidential memo warns as far back as January 2009 that educator cheating on 2008 standardized tests could have been widespread, with 191 teachers in 70 schools "implicated in possible testing infractions."

The 2009 memo was written by an outside analyst, Fay "Sandy" Sanford, who had been invited by then-chancellor Michelle Rhee to examine students' irregular math and reading score gains. It was sent to Rhee's top deputy for accountability.

The memo notes that nearly all of the teachers at one Washington elementary school had students whose test papers showed high numbers of wrong-to-right erasures and asks, "Could a separate person have been responsible?"

It recommends that DCPS contact its legal department "as soon as you think it advisable" and ask them to determine "what possible actions can be taken against identified offenders."

DCPS officials have said they take all cheating allegations seriously, but it's not immediately clear how they responded to Sanford's warnings. Only one educator lost his job because of cheating, according to DCPS. Meanwhile, Rhee fired more than 600 teachers for low test scores — 241 of them in one day in 2010.

...

In a statement, Rhee said she didn't recall getting Sanford's memo: "As chancellor I received countless reports, memoranda and presentations. I don't recall receiving a report by Sandy Sanford regarding erasure data from the (DC Comprehensive Assessment System), but I'm pleased, as has been previously reported, that both inspectors general (DOE and DCPS) reviewed the memo and confirmed my belief that there was no widespread cheating."

If any of this seems surprising, you either haven't been following Rhee's career or... Well, that 'or' is a bit complicated. Rhee has always done things that seemed questionable (abuse of power, suspect claims, relentless self-promotion) but these disturbing points were largely omitted from coverage that often verged on hagiography. It was only after giving her full support to the country's most reactionary governors that her reputation started to fade.

Even with that a surprising number of otherwise intelligent journalists who have covered Rhee for years still manage to deny the undeniable.

S&W appreciation day

A message from the makers of Swords and Wizardry in celebration of S&W appreciation day (April 17th):

We would like to ask you each to announce to all your readers that we will be offering a 1 day only 25% off Swords & Wizardry sale. The coupon and information is optional to post on your blog of course: Frog God Games (http://www.talesofthefroggod.com/) and d20pfsrd.com Store will be offering a 25% off Swords & Wizardry products.  We will be sending out a coupon code before the event.

No member of this blog is affiliated with this company nor do we have any financial interest.  But if you were planning to check this this system anyway, it is not a bad time. 

Note that a lot of the game system material can be downloaded for free, in a handy word document for house rules development.

When I say my to-blog list is ever-growing...

Good ones from Dean Dad and Adam Kotsko.

Felix Salmon is one of those rare business journalists who actually understands business.

Ebert was an odd Paulette.

WSJ is waaaaay behind the LA Weekly. (and when you can't keep up with those guys you really need to think about a career change).

"Fox threatens to become cable channel amid Aereo dispute" -- lots to say on this one.

An interesting story (via The Story) about a reporter who visited the markers the census department uses to commemorate the spot of the population centroid. I wonder what the centroids of population subgroups (demographic, economic, political) look like and how they've shifted over the years.

Another case of economists seeing a paradox when the rest of us don't?

Climate change comes with bumpy rides.

And finally, the film Paul Krugman doesn't want you to see.