Comments, observations and thoughts from two bloggers on applied statistics, higher education and epidemiology. Joseph is an associate professor. Mark is a professional statistician and former math teacher.
Tuesday, June 7, 2011
Sawdust in the transmission
Which gave me an excuse to dredge up another favorite bit of Southern pop culture...
[if you have trouble viewing this on your browser -- and thanks to Blogger you probably will -- you might want to view or download it at Internet Archive]
Trivia bonus points: Griffith has said this was his favorite episode.
p.s. This is a public domain copy that doesn't include rights to the theme. You might want to mute the first thirty seconds or so.
Monday, June 6, 2011
Yeah, n = 1, but based on this sample, I can't see Groupon doing any targeting at all
There was just one problem. In order to reverse engineer a model there has to be a model and I couldn't a trace of one. There was no indication that Groupon was using any information about me when they sent me an email. Here's an amusing but not unrepresentative example:
$125 for 24-Karat-Gold Specialty Facial and Chocolate Foot Scrub at Chocolat Day Spa in Arcadia ($260 Value) | |||||||||||||
| | ||||||||||||
The Company | Locations |
Of course, it's possible that I might give something like that as a gift (though I honestly don't think I know any women who would want a chocolate foot scrub -- the whole thing sounds disturbingly like a front for a fetish website), but when you have offers that the email recipient would never consider buying as anything but a gift, You can't really call it targeted marketing.
For further evidence that Groupon is not that sophisticated (or even that serious) about targeted marketing, check out the following:

The scary word here is "New." Did it really take over two years to add a feature that should have been fully operational the day the first website launched? Has Groupon actually neglected to gather rudimentary data on tens of millions of customers?
This might not be as bad as it looks (I don't see how it could be worse). Perhaps there's a level of sophistication that I'm missing. Unfortunately, as mentioned before, people who are betting on Groupon are assuming that the company will successfully pull off some extraordinarily difficult tricks with data. The apparent inability to manage simple tasks like gathering customer level demographics does not make these bets look all that smart.
p.s. Felix Salmon seems to mean something completely different by 'targeting' (though it's possible his definition is broad enough to include what I'm talking about here).
Sunday, June 5, 2011
What's the best investment you can ever make? (another Groupon post)
Just think about it for a moment. The returns are fantastic. There's almost no risk. The minimum investment is trivial. Your money is only tied up for a few days. You get your picture taken holding a big check. What's not to love?
Now, I can hear some of you negative types out there complaining about the difficulty of distinguishing between winning tickets and losing tickets (which are notoriously bad investments), but people routinely ignore these concerns when looking at the business plans behind IPOs. Why should you have a lower investing standard when dealing with your broker than you have at the 7 Eleven?
Take promises of targeted marketing. While it's true that almost all marketing is targeted to some extent and a few companies have been able to take that targeting to a relatively high level,* identifying customers who have a high likelihood (rather than a slightly higher likelihood) of buying something remains an extraordinarily challenging business problem. Most of the proposals you'll read that rely on solving that problem fall into the winning lottery ticket category.
Even with the recent explosion of consumer level data, the vast majority of plans to use targeted marketing run into one or both of the following problems: the lift provided by the selection method won't be large enough; the list produced won't be large enough.
Let's take the Groupon example. As pointed out here by Kaiser Fung, the merchants want new customers who are likely to become regulars. How would you go about targeting this segment? You might try matching the offer with the demographics of website the customers came in through, for instance, high end restaurants for people who came to Groupon through a New Yorker ad, but you'll still get lots responders who are already regular customers and more than a few bargain hunters (yes, even from the New Yorker). Or you could make offers only to people who have been identified as new to the area and are on the mailing lists of similar businesses in their old town, but I can tell you from experience, the number of names you'll get probably won't be large enough to bother with.
And Groupon has to thread an extraordinarily fine needle here. In most business situations, we might have a few customers who end up costing us a little money (for example, someone who just gets the loss leader at the drive-thru), but we're probably talking about fairly trivial amounts. In these cases, it's usually enough to build a model that distinguishes between responders and non-responder and fortunately, response is generally a quick and easy variable to measure reliably.
Groupon has to worry about non-responders (who are still associated with some costs), and about bargain hunters who use the offer then never come back (who cost Groupon's partners a substantial amount), and about regulars who use an offer for a visit they would have made anyway (who represent a double loss).
Separating all this chaff from the customers you want would be daunting even with the best of data and you will not have good data. How do I know? Because I've been there. I've dealt with third party data and I've written the hundreds of lines of SAS code needed to produce clean, usable data-sets. And I was only dealing with data from four or five sources, not trying to tease out a badly defined target variable from data collected from thousands of merchants. (remember, we're trying to identify customers who made their first visit using a Groupon offer and have since returned on their own dime.)
On top of all this, we're talking about a targeted marketing strategy that would have to work with everything from family pizza parlors to upscale wine bars, from pricey spas to summer camps, from teeth whitening to Scotchguarding (all of which have been recently offered by the company).
It's possible that Groupon will get around these problems but, until then, you might be better off with a scratcher-based portfolio.
* Of course, some people have proven pretty good at picking lottery tickets too.
More on Groupon
Our merchant arrangements are generally structured such that we collect cash up front when our customers purchase Groupons and make payments to our merchants at a subsequent date. In North America, we typically pay our merchants in installments within sixty days after the Groupon is sold. In most of our International markets, merchants are not paid until the customer redeems the Groupon.
Now you match this up with this, admittedly anecdotal example:
A good mate who owns a restaurant and did one of these deals after said it was outright amazing - many people would come in and spend EXACTLY the amount of the coupon. They didn't want to go 50c under and heaven forbid they went 50c over and have to pay more at full price
Even worse, you seem to have to more effects. One is a priming effect. New customers assume your $30 entree is worth $15. That is poison. The second is that merchants have begun to do things like "Groupon lines" (rational from their point of view to focus on the full-paying customers first) that reduce the value of the service.
So the business model involves a slow reimbursement to the merchant (waiting for money is death in a small business where cash flow issues can be fatal), enormous discounts (typically 75% off, with the last 25% coming in slowly), and "bargain hunters" who are unlikely to become regular customers.
As a final point, consider:
Perhaps Groupon management thinks it is creating a sustainable Prisoner’s Dilemma, one that ultimately destroys value for the local merchant ecosystem but benefits Groupon. In other words, Groupon could grow so big that local merchants have to use it, even though it ultimately hurts them. In game theory terms, Groupon creates an equilibrium point at “All Local Merchants Defect,” and then, having forced merchants into this value-destroying equilibrium, takes a cut for having rigged the game. Obviously, Groupon couldn’t share this thinking publicly. They would just continue to use the attract-loyal-new-customers argument even though it no longer makes any sense for a ginormous Groupon.
This may sound cynical. But if this is Groupon’s game plan, it isn’t cynical. It’s naïve. Most local merchants simply don’t have enough value in their collective ecosystem to share anything remotely like this much value with Groupon. This isn’t a stable equilibrium, it’s a suicidal one. The local merchants will have to stop using Groupon en masse not long after they first start experimenting with it.
The only way this works is if process quadruple for restaurants (because everyone uses a groupon). Maybe more than quadruple because you replace cash in hand with a 60 day payment. Why would restaurants not break this equilibrium and offer 60% off if you show up without a groupon? Immediate cash in hand, much higher profits, the customer pays less and they don't have to buy a groupon in advance.
And if you don't get this type of prisoner's dilemma, then it is hard to see where the sustainable value is going to be in this business model when your clients will eventually hate you.
Friday, June 3, 2011
Salmon/Fung cage match -- Did Salmon use a representative example?
Fung (who shares my high opinion of Salmon's acumen) has a good take-down of Salmon's analysis. You should probably read the whole thing but there's one particular aspect that strikes me as requiring additional attention.
Here's Fung:
Of course, that $7.50 doesn't take into account the cost to the restaurant of preparing and serving the meal (which would further help Fung's case), but putting that aside, how likely are customers to overshoot by a factor of three?Let's start with [Salmon's] neighborhood restaurant example:
At Giorgio's, for instance, diners paid $15 for their Groupon -- which gave them $30 of food. But dinner for two at Giorgio's, with some kind of alcohol, can easily run to $100 or more. So even after knocking $22.50 off the bill (remember that Giorgio's kept $7.50 of the proceeds of Groupon), the restaurant would often still make money.
This is a bit complicated. We can trace how the cash flows. For Groupon, diners pay them $15, and they keep half of that, $7.50. For the diners, they paid Groupon $15 (now worth $30 spending), and so they pay Giorgio's $70; in other words, they paid $85 out of pocket for a meal worth $100 without Groupon. Giorgio's take in $70 from the diners plus $7.50 coming from Groupon for a meal worth $100.
...So, I don't think the Groupon model is the kind of slam dunk Felix seems to think it is. Only if certain conditions are met will the merchants gain anything from Groupon:
- the value of the coupon has to be a fraction of the total spending at the merchant; in this example, the diners spent more than 3 times the face value of the coupon. What if the diners spend exactly $30? Then Giorgio’s loses $22.50 on each regular customer and earns $7.50 on each new customer, meaning that every 3 new customers pay for each regular’s discount. Not very attractive numbers at all.
Looking at the offers currently on Groupon, I see three restaurants, Beto's Grill ($20 for $10), Stefano's Pizzeria ($20 for $10) and Henry's Hat ($35 for $15). Of the three, I'm only familiar with Henry's Hat (a game themed bar that, last time I was there, had Kruzno in its library), but, based on the information online, it would be fairly easy for two people to keep the tab down to close to the amount of the Groupon offer in all three.
Obviously, there are plenty of places in LA where you should plan on paying big money for your dinner, but I haven't noticed those places on Groupon. Instead I've seen a lot of moderately priced spots, and I doubt you've got a lot of couples running up a $60 dollar tab on three buck a slice pizza.
Apparently, journalists who work for Yahoo don't have access to the internet
In Little Rock, Arkansas, for instance, the 2010-2011 yearbook at Russellville Middle School lists the "5 worst people of all time." Students listed former President George W. Bush and Bush's vice president, Dick Cheney, right after Adolph Hitler, Osama Bin Laden and Charles Manson.Superintendent Randall Williams asked the yearbook printing company to cover the list with pieces of tape, but many parents aren't mollified.
"I think it's just hard to explain, and I've talked to the sponsor and she is very very very upset about it. That she didn't pay any attention to that particular part of that particular page," he told the local Fox affiliate. "I think she maybe just scanned the whole page and went on."
Friday afternoon data dump
There is nothing so distinctly middle-brow as the fear of being middle-brow -- yet another TNR edition.
In this excellent NPR piece, advocates claim this test can identify psychopaths but the researcher who developed the test isn't comfortable with the way it has been used. Lots of interesting stat questions here.
I always feel nervous when I disagree with Felix Salmon's analysis of a business model but Kaiser Fung made me feel a little better about this one.
Also from Gelman: If I can find the time, I'd like like to delve into this story about perennial nut-case Satoshi Kanazawa; I'd also like to join in the discussion of this Tyler Cowen post.
I wonder if this TNR writer knows that this practice goes back at least to Hearst (and was the basis for the Hitler allusion in Citizen Kane).
More reasons from Ebert to hate 3D.*
When a rocket scientist I know (this is LA, they're all over the place) heard an interview with James Surowiecki about the Wisdom of Crowds, he commented "wow, they've just discovered standard error." Perhaps now people are starting to realize some of the limitations. There's just not a lot of there there.
*update: Ebert has another post up on the search for the next big thing. His thoughts on the changing economics of the industry are particularly relevant.
Time will tell. What depresses me is that mainstream Hollywood seems to be experiencing a crisis of confidence. For decades there was the faith that if you released a good movie, people might very well buy tickets to it. The traditional pattern was to open it slowly, hope for good reviews, and then "roll it out" more widely.The economics of television advertising put an end to the theory that an audience might find a movie. Now the movies must find an audience. Big new releases open everywhere at once, and everybody knows they will be available before long on DVD or On Demand . Theaters offer 3D as something you can't get at home (apart from "3D television," about which I am unpersuaded). Now we get rocking and rolling D-Box seats.
One more thought
One thing that I think was interesting, though, was his decision to be defiant about his career. Comments like:
Why do I put “worked” in quotation marks? Because my main task as a university professor was self-cultivation: reading and writing about topics that interested me. Maybe this counts as work. But here I am today—like many of my retired colleagues—doing pretty much what I have done since the day I began graduate school, albeit with less intensity.
Seemed to me to be extremely revealing. I think that one possibility is one of culture. I grew up in a social democracy and I would feel shame if I thought I was "milking the system". My father used to explain the low Swedish unemployment rate to me as being a cultural phenomeon (in Sweden the shame of not working is high).
On the other hand, I occasionally see people bragging about how they bilked the system as if this is a point of pride and not deep humiliation. I wonder if there is a cultural divide here as I would find behavior to be shameful. Consider this statement:
Committee meetings were tedious but, except for the few good departmental citizens, most of us were able to avoid undue burdens.
Why would he not be ashmaed not to have been a good departmental citizen? I am always worried that I am not carrying enough administrative burden in my department and concerned when another faculty member is overloaded.
Or this comment:
To be sure, some of my colleagues were prodigious researchers, devoted teachers, and outstanding departmental, university, and professional citizens. But sociologists like to talk about what they call the “structural” constraints on behavior. While character and professional ethics can withstand the incentives to coast, the privileged position of a tenured professor guarantees that there will be slackers.
So why are character and professional ethics not valued? Why does an confession as to a lack of professional ethics sound like an attack on the profession and not an admission of a personal failing. Mark pointed out the comments on his teaching ability and I have to admit it sounds like he wasn't the most focused professor ever.
Or perhaps I misunderstand some parts of this situation??
Thursday, June 2, 2011
University Professor Compensation -- Andrew and Joseph hit the big points but leave out the punch line
You'll have to go to the second page to find a 'good' rating (the rest were 'poor'):
got a B in his class. tests are all fill in the blank/short answer but you can use the book and your lecture notes. so you really have to come to lecture and take good notes. he is really disorganized and got off topic easily. i wouldn't recommend him.
DO NOT TAKE THIS CLASS W/HIM. Terrible teacher!! He is very frustrating and unclear. Nobody understands what he is talking about. Everyday he comes in with an empty coffee cup and takes sips throughout the class even though there is nothing in his cup!!! CRAZY. DO NOT TAKE SOC 100 WITH HIM! HE IS SO UNORGANIZED!!!
This class can sometimes be interesting, but mostly he just rambles about useless stuff that barely makes sense. He doesn't even write a real syllabus he's so disorganized. If you take his class, definitely go to lecture. You'll fail completely if you don't.
i love this class. If you're right wing lol, i think you are going to like professor rubinsteinIf you read between the lines, that review doesn't really contradict the others. Numerous students complained about the professor going off topic. Since it's hard to imagine a straightforward 'intro to sociology' lecture having a deeply right wing bent, it seems more likely that the good review was also a reaction to these tangents.
When Rubinstein talks about how overpaid he is, he's almost certainly right, not because the system is flawed (that point is certainly up for discussion) but because David Rubinstein appears to be an exceptionally bad teacher.
We may be seeing the beginning of a new journalistic genre: writers proudly basing arguments (implicitly or explicitly) on their own incompetence. First we got the "I'm too financially inept to support a family on $350,000 a year" stories (and the closely related "I'm too financially inept to support a family on just over a quarter of a million and too financially illiterate to grasp the concept of marginal tax rates"). Now we get Rubinstein. Can we expect some columnist to follow with a piece entitled "You shouldn't trust journalists because I'm a moron"?
(actually, I'd like to see that last one.)
University Professor Compensation
After 34 years of teaching sociology at the University of Illinois at Chicago, I [Rubinstein] recently retired at age 64 at 80 percent of my pay for life. . . . But that's not all: There's a generous health insurance plan, a guaranteed 3 percent annual cost of living increase, and a few other perquisites.
In my 34 years, just one professor in the sociology department resigned to take a nonacademic job. For open positions, there were always over 100 applicants, several of them outstanding. The rarity of quits and the abundance of applications is good evidence that the life of the college professor is indeed enviable.
Protests against efforts to reform pay scales, teaching loads, and retirement benefits employ a “solidarity forever, the union makes us strong” rhetoric. What these professors and other government workers do not understand is that they are not demanding a share of the profits from the fat-cat bourgeoisie. They are squeezing taxpayers—for whom the professors purport to advocate—whose lives are in most cases far harsher than their own.
I have a few comments to make about this particular issue. First of all, I notice that the professor in question is happy to brag about his success but is not proposing, for example, to stop accepting his pension. I am not sure why it makes sense to mock the people who support one's financial position. Is it considered good sense to mock customers in business?
Second, there are a lot of people in all fields of endeavor who do not earn their salary. What is it about academics that makes people think it might make sense to brag about being a poor performer?
Third, why is the focus on the cost to the taxpayer for academic pensions a focus? We subsidize a lot of activity -- for example, we tax hedge fund managers at captial gains tax rates. This is a very important subsidy on that activity but we do not hear comments about how hard it is for people in the working class to subsidize multi-billion dollar incomes.
I think Andrew Gelman makes the winning point here:
David Rubinstein appears to be somewhat of an extreme case of the underworked and overpaid professor: he taught at a low-ranked but high-paying institution, he got his Ph.D. at a time where they were giving out tenure-track slots like candy canes at Christmas, he (by his own admission) spends a total of less than one hour per week on class preparation, grading, and advising combined, and he got a contract in an era with generous retirement benefits.
It is unclear to me what action makes sense here, given these issues. Clearly, attacking current new professors does not seem to address the core issues (that David Rubinstein was hired in an exceptional era). It can only hurt people who have had to struggle up under much more difficult circumstances than he has. Which seems to be identical to his critique of academics in general (that they are priviledged and don't care about people who have had to deal with more difficult life circumstances).
I do know that my own experience of university life is completely different. I am in a resaerch position and I still spend a lot more time on teaching then he does, not to mention leading student research groups. My pension is defined contribution and my pay has just been cut as part of a state-wide austerity movement (after 1 year, that time when compounding means cuts hurt the most). It's hard work but I like the job. I do know that when I worked in industry, pay was higher and life was a lot less stressful.
It is a very odd article.
Wednesday, June 1, 2011
Tyler Cowen argues against more regulation with an example that calls for more regulation
In case you haven't been following this story, Google has been getting a lot of press for its experiments with self-driving cars, especially after statements like this from Stanford professor Sebastian Thrun:
"Think about the car as a medium of mass transit: So, what if our highway-train of the future meant you go on the highway, and there's a train of very close-driving cars with very low wind drag, fantastic capacity, is twice as efficient as possible as today, and so there is no congestion anymore?"Cowen is clearly thinking along the same lines:
Furthermore, computer-driven cars could allow for tighter packing of vehicles on the road, which would speed traffic times and allow a given road or city to handle more cars. Trips to transport goods might dispense with drivers altogether, and rental cars could routinely pick up customers. And if you worry about the environmental consequences of packing our roads with cars, since we can’t do without them entirely, we still can make those we use as efficient — and as green — as possible.Putting aside the question of the magnitude of these savings in time, road capacity and fuel effeiciency (which, given the level of technology we're talking about here, aren't that great), where exactly are these savings coming from?
Some can certainly be attributed to more optimal decision-making and near instantaneous reaction time, but that's not where the real pay-off is. To get the big savings, you need communication and cooperation. Your ideal driving strategy needs to take into account the destination, capabilities and strategies of all the vehicles around you. Every car on the road has got be talking with every other car on the road, all using the same language and rules of the road, to get anything near optimal results.
Throw just one vehicle that's not communicating (either because it has a human driver or because its communication system is down or is incompatible) into the mix and suddenly every other vehicle nearby will have to allow for unexpected acceleration and lane changes. Will driverless cars be able to deal with the challenge? Sure, but they will not be able to able to do it while achieving the results Thrun describes.
A large number of driverless cars might improve speed and congestion slightly, but getting to the packed, efficient roads that Cowen mentions would mean draconian regulations requiring highly specific attributes for all vehicles driving on a major freeway. The manufacture and modification of vehicles would have to be tightly controlled. Motorcycles would almost certainly have to be banned from major roads. Severe limits would have to be put on when a car or truck could be driven manually.
This would seem to be another case of a libertarian endorsing a technology with less than libertarian implications.
Tuesday, May 31, 2011
A couple of interesting stories on the business of gambling
By comparison, the AP has this account of a casino model that players have remarkably little interest in. Given the emergence of casinos in nearby states and the stagnant economy, the decline in Atlantic City isn't exactly unexpected, but this piece is still worth checking out and the title "Monopoly lost: Atlantic City's rise and fall" is definitely good for some bonus points.
A "how to lie with statistics" instant classic from the Wall Street Journal op-ed page
And, as Andrew Sprung points out, that's still lower than the rate under Ike. It would be interesting to see how Moore reconciled the high taxes of the Postwar Era with its phenomenal growth.The question-as-headline is your second red flag that this just might be a deeply disingenuous op-ed (the first is that it’s on The Wall Street Journal op-ed page):
A 62% Top Tax Rate?The top marginal tax rate is just 35 percent now, of course. So how does Moore come up with the idea that Obama and the Democrats are pitching a 62 percent tax rate for the rich? Disingenuously.
First, here’s a classic example of misleading readers with an apples and oranges comparison:
If the Democrats’ millionaire surtax were to happen—and were added to other tax increases already enacted last year and other leading tax hike ideas on the table this year—this could leave the U.S. with a combined federal and state top tax rate on earnings of 62%. That’s more than double the highest federal marginal rate of 28% when President Reagan left office in 1989. Welcome back to the 1970s.For Moore’s headline purposes he includes state taxes to get to 62 percent, but when he compare it to rates under Reagan, he doesn’t include state taxes.
The comparison is much more misleading than that, really. Moore is also including things like payroll taxes to come up with his fake 62 percent number, while not including them in that 28 percent Reagan figure. You can’t do that, boss.
Moreover, to come up with that doozy of a number, Moore is adding in not only state and payroll taxes, but just about every possible tax hike being bandied about by Democrats. But Moore knows full well that even if they wanted to, which they don’t, the Dems wouldn’t be able to enact every one of these. But he acts like they’re all coming.
Those theoretical and far-from-likely tax hikes include a 3 percent surtax on incomes over a million bucks; Obama’s proposal to end the Bush tax cuts for the rich in 2013, which would return marginal rates to 39.5 percent at the top; 3.4 percent Medicare taxes (Moore includes the employer’s contribution here); and 10.1 percent in additional payroll taxes because “Several weeks ago, Mr. Obama raised the possibility of eliminating the income ceiling on the Social Security tax” (that includes the employers’ share, too, though Moore doesn’t say that).
There’s also this:
Today’s top federal income tax rate is 35%. Almost all Democrats in Washington want to repeal the Bush tax cuts on those who make more than $250,000 and phase out certain deductions, so the effective income tax rate would rise to about 41.5%.It’s unclear how Moore gets to 41.5 percent here. Repealing the Bush tax cuts would return the top marginal rate to 39.5 percent. Deductions affect effective tax rates, which are far lower than marginal rates. Since he doesn’t explain it, and since the backdrop is the rest of this misleading piece, I’m going to assume that this 41.5 percent number is false (I believe Moore is talking about the PEP and Pease taxes, but those don’t apply to people making more than $525,000, so they can’t be included in a total tax rate that includes a millionaire’s surtax.)
To get to 62 percent, Moore also includes 4 percentage points for state taxes. It’s unclear why he didn’t include local taxes while he was at it. That would have got him another full point (it’s always worth noting that state and local taxes are extremely regressive, taking 11 percent of the income of the lowest quintile of earners, which is more than twice what the top 1 percent pays.)
All this allows Moore to plant the zombie lie that Democrats are “proposing rates like those under President Carter.” Even with all his hocus-pocus, that’s not true, either. The top marginal federal income tax rate under Carter was 70 percent, a full eight percentage points higher than Moore’s fake number. If you include all the state and payroll taxes he uses to get to Obama’s “62 percent” figure, which you have to to make the comparison, that Carter number would be closer to 80 percent.
Probably not informative, but interesting.
Metaphor of the day
If a project doesn’t have an owner, it’s like a chainsaw on a rope swing. Why would anyone even go near that?
[Technically a simile, but do you really want to get technical here?]