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.
Sunday, September 18, 2011
How do you say Los Angeles
Loss AN-ju-less versus Loss AN-guh-less: did they pick correctly?
Saturday, September 17, 2011
What is up with Arkansas?
But nothing is as shocking as how badly the for-profit institutions do. I think some sober looks at these numbers make sense before we conclude that for profit is automatically better, especially given that student debt is large and can no longer be discharged by bankruptcy.
Thursday, September 15, 2011
Medical spending as a zero-sum game
Definitely worth a look.
Professionals and Advancement
With almost all careers, we expect a certain level of ratcheting advancement. We generally assume that if we maintain a certain quality of work, we will see a more-or-less steady increase in either our compensation, our employability or our job security. This advancement can take all sorts of forms from traditional promotions to a salesman's contact list to a writer's readership, but whatever the form, it is exceedingly rare to find jobs where you start each year about where you started the last one and it's next-to-impossible to find one that would be considered a 'profession.'
(Of course, there are many freshwater economists who are deeply uncomfortable with this ratcheting effect, who would argue that an ideal labor market should have no memory, that the services provided by a long time employee should be treated no differently than any other commodity. Long time OE readers will probably know I don't agree with the idea that labor should be treated as just another market, but that's a topic for another time. For now we're talking about the way things are.)
The discussion of teacher compensation and job security has almost entirely ignored the larger question of advancement, looking at the unusual contractual protections afforded the profession but failing take into account the equally unusual limitations. Take a minute and try to think of professions that have the following career constraints:
Few opportunities to move up the org chart. Not only is the structure here relatively flat, but unlike many industries, the move to management is almost a complete break from your previous role. Thus 'rewarding' the best teachers by making them administrators is a questionable strategy. We obviously need exceptional principals but we can't have teacher career track focused on taking the best teachers out of the classroom;
Non scalable work. Even if you accept claims about class size not mattering (and there's a lot to dispute in the reasoning behind those claims), there are still hard limits to the number of fourth graders one person can teach in a year. Compare this to someone like a journalist who can, in a sense, sell the same piece of work a virtually unlimited number of times;
Bounded compensation. Though movement reformers talk a lot about different incentive pay plans, pretty much all of them are metric based and have pre-determined maximums;
Lack of entrepreneurial opportunities. It is true that administrators can go out and start their own charters but teachers can't start their own classes;
Limited chances for promotion through relocation. This does happen but it's discouraged with good reason. The winners tend to be high-income suburban schools. Add to this the logical results of movement reforms that effectively reduce job security for teachers in schools bad neighborhoods and you have a huge incentive to actually widen the achievement gap.
In other words, we have here another case of advocates for business-based solutions who don't understand how businesses actually operate. Not coincidently, this is also an area where conservatives with actual business experience (like Jim Manzi) tend to take more nuanced positions.
Appropriate Scales
On the other hand, very small variations can look large if the axes covers only the range of variation. The real piece of information that is missing is what is the size of a meaningful change. Maybe we should have graphs declare this extra piece of information so that this point can be discussed along with the variation shown in the graph, itself,
The Wisdom of Salmon
What’s more, everybody wants to be invested in stocks when the market’s going up — just not when it’s going down. Is it possible to actively manage your 401(k) so that you try to go long stocks when they’re going up and then move to cash or bonds when stocks are falling? Well, you can try. But that’s called timing the market, and it tends to end in tears. You are not a hedge-fund manager, and even they get these things wrong. Don’t think you can time the market, because you can’t. So if you want to be invested in up markets, you have to be invested in down markets, too. And as the chart shows, your retirement account will tend to grow most of the time anyway.The main reason for this is that we’re not just sitting back and hoping that the stock market will do all the heavy lifting. Every paycheck, we’re putting money into our 401(k) accounts — about 8.7% of what we earn, on average. And so every quarter, we see our balance rise not just because we’re great at investing, but also because we’re manually adding to the pot.
And in fact that second aspect of saving for retirement is significantly more important — and much more under our own control — than the first aspect. When it comes to our 401(k) plans, people tend to focus far too much on the quarter-to-quarter fluctuations in mark-to-market asset value, rather than trying simply to save as much money as they can for when they’re older. My advice is to think of a retirement account like a piggy bank: you put money in there on a regular basis, and eventually it grows to a substantial sum. Once it’s in there, of course, you try to invest in something reasonably sensible — target-date funds are a pretty good idea, so long as their fees are low. But you don’t have much control over the internal returns on your retirement funds; you do have control over how much you save. So concentrate on the latter more than the former.
The Growth Fetish
It's obvious that our economy is suffering from a lack of growth but for a while now I've come to suspect that in a more limited but still dangerous sense we also overvalue growth and that this bias has distorted the market and sometimes encouraged executives to pursue suboptimal strategies (such as Border's attempt to expand into the British market).
Think of it this way, if we ignore all those questions about stakeholders and the larger impact of a company, you can boil the value of a business down to a single scalar: just take the profits over the lifetime of a company and apply an appropriate discount function (not trivial but certainly doable). The goal of a company's management is to maximize this number and the goal of the market is to assign a price to the company that accurately reflects that number.
The first part of the hypothesis is that there are different possible growth curves associated with a business and, ignoring the unlikely possibility of a tie, there is a particular curve that optimizes profits for a particular business. In other words, some companies are better off growing rapidly; some are better off with slow or deferred growth; some are better off simply staying at the same level; and some are better off being allowed to slowly contract.
It's not difficult to come up with examples of ill-conceived expansions. Growth almost always entails numerous risks for an established company. Costs increase and generally debt does as well. Scalability is usually a concern. And perhaps most importantly, growth usually entails moving into an area where you probably don't know what the hell you're doing. I recall Peter Lynch (certainly a fan of growth stocks) warning investors to put off buying into chains until the businesses had demonstrated the ability to set up successful operations in other cities.
But the idea of getting in on a fast-growing company is still tremendously attractive, appealing enough to unduly influence people's judgement (and no, I don't see any reason to mangle a sentence just to keep an infinitive in one piece). For reasons that merit a post of their own (GE will be mentioned), that natural bias toward growth companies has metastasised into a pervasive fetish.
This bias does more than inflate the prices of certain stocks; it pressures people running companies to make all sorts of bad decisions from moving into markets where you don't belong (Borders) to pumping up market share with unprofitable customers (Groupon) to overpaying for acquisitions (too many examples to mention).
As mentioned before we need to speed up the growth of our economy, but those pro-growth policies have to start with a realistic vision of how business works and a reasonable expectation of what we can expect growth to do (not, for example, to alleviate the need for more saving and a good social safety net). Fantasies of easy and unlimited wealth are part of what got us into this mess. They certainly aren't going to help us get out of it.
Tuesday, September 13, 2011
Dream a little dream for me
It's a funny story but it has a serious undercurrent. At the risk of sounding like an alarmist, I'm beginning to think that our discourse, our ability exchange and evaluate important information and use it to collectively make informed decisions is in serious trouble, and I'm not sure how you can run a democracy without that.
The decline in journalistic professionalism is a big part of that problem. There are some excellent journalists out there, but there are also far too many like the ones in this story. They nonchalantly build on each other's fictions. They unquestioningly accept claims from interested parties. They dodge responsibility for uncomfortable facts by hiding behind he said/she said stories.
As I've said before, I honestly believe that given good information, the American public tends to make good decisions but there's a corollary to that claim: given the crap we've been fed recently, it's a wonder we still have a country.
And now for a break from serious discussion
Imagine a host talking to a panel of four pundits about someone about to roll a 6-sided die.
Host: What's your prediction for the big dice roll?
Judy: Well, Jim, I've knocked on thousands of doors in this province, and families everywhere are telling me the same thing. They like the number 1, so I expect it to do really well.
Bill: Remember, the big dice roll is taking place on a Sunday after church, so the smart money is on 3, the trinity. We all remember Easter Sunday 1985 when a three was rolled three consecutive times. History is on the side of 3.
Jim: Look at the data. An even number has come up on 9 of the last 13 rolls. You have to play the hot hand on this one and go for 2, 4, or 6.
Alice: I agree with Jim's data, but all that means is that odd numbers are due. Judy is right that 1 is the trendy pick, but I really like 5 as a dark-horse candidate.
[Off-screen a mathematician is sobbing].
And, I suppose, a casino operator is gloating . . .
401(k) plans
The tax break for defined contribution retirement plans will cost the Treasury $212.2 billion between 2010 and 2014, according to the Joint Tax Committee. But the vast amount of that benefit - as much as 80 percent - goes to the top 20 percent of earners, according to estimates from the Tax Policy Center, a nonpartisan, but liberal-leaning, think tank.
For example, a person in the 35 percent tax bracket saves $35 in taxes every time he puts $100 in his 401(k), for a net cost of $65. Someone in the 15 percent bracket pays $85, after tax, for the same $100 contribution. The Pension Rights Center, which has favored traditional defined benefit pensions and other programs aimed at lower-income retirees, advocates rolling back the current $16,500 annual 401(k) tax-deferred contribution limit to the $10,500 level it was at before the Bush tax cuts, its director, Karen Ferguson, has said.
One way to address both the cost and the disparity is to change the deduction into a credit. William Gale, of the Brookings Institution, will present a plan like that to the Senate committee on Thursday. His plan would eliminate the deduction entirely and replace it with a federal match that would be deposited directly into workers retirement accounts. A match of 30 percent would be revenue neutral, he says.
Neither solution is ideal. Lowering the deduction limit makes these plans less able (even in theory) to store enough wealth for retirement. It also makes "catching up" after a period of unemployment or education more difficult.
Matches, on the other hand, are much easier to cut than tax breaks. Dropping the match from 30% to 28% is an easy cut that raises a lot of revenue. It may be harder to penalize post-tax withdrawals, which runs the risk of funds being emptied due to an unexpected job loss.
None of this would really matter if we were confident that social security would be around. It really is the key government anti-poverty program. But ponzi scheme comments are not helping build confidence in the long term health of the program.
Sunday, September 11, 2011
Personal Finance talk
Let’s add up how much of the iMac, iPod, iPhone, iBook and iPad profts have been paid out to the owners of Apple. Well lets think. . . oh yes I have it now, ZERO DOLLARS! Not one single penny.
So far is this really different from what Allen Stanford did? I hear some of his investors actually got redemptions. But, I am sure Apple investors will get their money some day, right.
They have the value of their share of the company, but that might very well be spent on other things before any dividends are paid. It's scary to consider.
Even worse is his discussion of Sir Alan Sanford:
You can do whatever you want to Allen Stanford. He is now broke. He got beat up in prison. He may very well spend the rest of his life there. But, he’s 61 years old now. These experience were his life. You can’t take that away.
Once you realize that, you realize the fundamental vulnerability that everyone has in handing over your assets to someone else. There is just no recourse against the other person consuming them.
You have to trust and that’s at the heart of what call The Big Externality.
That is a lot more scary. It really makes the idea of a government sponsored pension program way more appealing. And it definitely makes one skeptical about the ability of a typical investor to manage their assets. After all, I would not have seen Apple as an atypical investment vehicle, mostly because I like and consume their products. But if they are not paying dividends, then the idea behind getting money out of them is entirely to sell shares to somebody else.
But why would they want to buy them if they do not produce returns?
Saturday, September 10, 2011
Remind me not to piss off Felix Salmon
What Robinson nails is the way that this is what Scaramucci does — it’s his job. Scaramucci is a fund-of-funds manager, posting returns even he admits are lackluster: he more or less tracks the S&P 500, while making big, risky bets (a third of his assets are in MBS), investing in leveraged hedge funds, and reserving the right not to redeem his clients’ money upon request. Which means that he only has two ways to make money: either find stupid people to give him their money, or else shower himself with so many conspicuous indicia of success that people just want to buy into his perceived success.
OK, make that one way to make money.
It’s far from clear that Scaramucci actually is successful, in financial terms, by Wall Street standards. He certainly spends a lot — millions of dollars — on various forms of conspicuous consumption and self-promotion. But he’s not making a lot: since he’s a fund-of-funds manager, he’s making 1.5-and-zero, rather than 2-and-20. And under the terms of his deal with Citigroup, a substantial chunk of that 1.5 goes straight to them. He has to run Skybridge, of course, with all the employee compensation, compliance costs, and the like that entails. He’s regularly writing seven-figure checks to pay for things like the Davos Tasting of ludicrously expensive wine. And of course he has to pony up charitable donations, too, so as to be able to get up in front of a well-heeled crowd to receive the Hedge Funds Care Award for Caring. (I’m not making this up.)
Scaramucci’s fake-it-till-you-make-it approach might end up working: his fund is still growing, and Robinson says that he “has become the Wall Street player he aspired to be when he first landed at Goldman some 22 years ago.” He’s living proof of what Windward Capital’s Robert Nichols is quoted saying at the end of the article: “Performance isn’t what beats a path to your door. It’s sales and marketing.”
But he’s not a stock-picker, or even, really, a hedge-fund manager: he just plays one on TV.
Type M Bias
And classical multiple comparisons procedures—which select at an even higher threshold—make the type M problem worse still (even if these corrections solve other problems). This is one of the troubles with using multiple comparisons to attempt to adjust for spurious correlations in neuroscience. Whatever happens to exceed the threshold is almost certainly an overestimate.
I had never heard of Type M bias before I started following Andrew Gelman's blog. But now I think about it a lot when I do epidemiological studies. I have begun to think we need to have a two stage model: one study to establish an association followed by a replication study to estimate the effect size. I do know that novel associations I find often end up diluted after replication (not that I have that large of an N to work with).
The bigger question is whether the replication study should be bundled with the original effect estimate or if it makes more sense for a different group to look at the question in a separate paper. I like the latter more as it crowd-sources science. But it would be better if the original paper was not often in a far more prestigious journal than the replication study, as the replication study is the one that you would prefer to have the the default source for effect size estimation (and thus should be the easier and higher prestige one to find).
Friday, September 9, 2011
Replication in Science
The unspoken rule is that at least 50% of the studies published even in top tier academic journals – Science, Nature, Cell, PNAS, etc… – can’t be repeated with the same conclusions by an industrial lab. In particular, key animal models often don’t reproduce. This 50% failure rate isn’t a data free assertion: it’s backed up by dozens of experienced R&D professionals who’ve participated in the (re)testing of academic findings.
Of course, I worry even more about softer disciplines where the difficulties of replication are much higher (you don;t just have to replicate a lab, you may need to develop an entire new cohort study).
Scary stuff.