Misc: July 2007 Archives

 

July 26, 2007

The IETF Social was held Tuesday night at the House of Blues which is, as we all know, the hippest place in Chicago. Anyway, I'm there eating my pulled pork sandwich when some guy dressed in a cop uniform gets up on stage and announces that there are some dangerous fugitives in the audience, apparently dressed like uh, Hasidic diamond merchants. OK, OK, Dan Aykroyd owns the place so a little tribute sort of has to be expected, but then next thing I know the MC is announcing Cab Calloway, who, when I look over, appears to be somewhat younger, fatter, and less dead than I remembered him. He, of course, sang Minnie the Moocher.

This was followed by two vaguely Dan Aykroyd and John Belushi looking guys in dark suits singing what I believe to be the Blues Brothers set from the Palace Hotel Ballroom on the shores of Lake Wazzapamani. Now, I bow to few in my admiration for the genius of The Blues Brothers (27 years old now!), but when exactly did House of Blues cross over the line between tribute and parody?

 

July 23, 2007

Over at Yglesias, people are discussing this anti-universal health care ad:

A number of the commentors observe that this is a bit inartful, since movie theaters are not exactly bastions of state ownership. For instance:

Soooo...movie lines are government run? Movie tickets are Federally subsidized and not a matter of free-market supply and demand?

OK, so this is sort of a fair cop, since the advertisers brought up the comparison, but at some level these are different situations, or at least maybe are.

Queues serve two primary social purposes: exerting backpressure on demand and distributing load over time.

Exerting Backpressure on Demand
It doesn't take a queueing theorist to see that if a system can service 10 users an hour, then if the aggregate number of aggregate customers entering the system is 20 an hour on a permanent basis, then not all of them are going to be served. There are a lot of different ways to deal with this (rationing, auctions, etc.), but one is simply to implement a first-come-first-served policy. Everyone who can't be served immediately just has to wait in the queue. Now, if your aggregate demand exceeds your aggregate service capability, that means that the queue gets longer and longer. At some point, new users decide that they're not going to get served in any reasonable time and don't even bother to enter the queue. This provides a form of load management, sorting users to some extent by their willingness to wait. So, making people queue is one way of dealing with demand which would otherwise exceed capacity.

Load Distribution
The other major purpose queueing is load distribution. Lots of systems have extremely uneven demand profiles. If you average demand over time, it's less than the capacity of the system, but over short periods of time it significantly exceeds demand. You can of course deal with this by increasing capacity, but generally you just make people wait during periods of high demand and then catch up when demand is low. This lets you handle a plausible level of service even when you can't handle peak demand.

The flip side of load distribution—and this is where we get back to movie theaters—is that there are systems where the rate of service provision is extremely variable. In particular, any given movie theater room is only showing one movie at a time and people are only admitted every two hours or so. If that's at 12 PM, 2PM, 4PM, etc., and someone shows up at 1PM, they have to wait till 2 to get into the theater. This is true even if aggregate capacity far exceeds demand, i.e., the theater is always half empty. Even if people all show up at 1.59, only so many people can fit through the theater door at once, so you still end up queuing a bit. Now, obviously you could have 10 times as many movie theaters, thus reducing the amount of queuing, but nobody expects theaters to operate at 100x levels of overcapacity. It is worth noting, though, that there's a tradeoff between overcapacity (i.e., idleness) and forcing users to queue.

Now let's take the case of medical service, which is more complicated. When people talk about waiting for medical service, they're mostly using queuing as synechdoche for the system being overloaded and queuing as a form of pushback on demand. The implied claim, of course, is that free markets don't have this. Whether that's true or not (and if you were in Palo Alto on iDay you know it's not) queuing at movie theaters isn't that great a counterexample.

 

July 10, 2007

About 4 months back I received a notice informing me that I had been selected for jury duty. [Strangely, I've lived in California for 15 years and never been selected, whereas I know people who've been selected multiple times. I don't have any statistical data and clearly random results can look like they have patterns, but I still wonder about the quality of their PRNG.] It intersected with a time when I was scheduled to be in Barcelona giving a talk so I availed myself of the one-time deferral. Of course this turned out to be a mistake because I was of course just as busy the new week they scheduled me for....

In case you have never had jury duty in Santa Clara county, the system works like this. You're required to be available all week but you're only on "standby". This means that you get a jury group number and have to call a number or check a Web site to see if you have to come in. Here's how this works:

  1. The letter says "check back Friday after 5 for instructions".
  2. Friday at 6 you check and it says "check back Monday between 11 and 12."
  3. Monday at 11 you check and it says "check back Monday after 5."
  4. Monday after 5 you check and it says "check back Tuesday between 11 and 12."

Lather, rinse, repeat.

I actually managed to make it through the whole week this way without ever having to go to the courthouse. I guess that's good, but on the downside I could never plan more than a few hours ahead and had to inconvenience a bunch of people who wanted to meet with me when I had to keep saying "I could maybe meet first thing in the morning but I won't know till after 5". I'm to

I found the whole process really inconvenient and I've heard from others that they had the same experience. I would have much rather just had to spend a single day at the courthouse but be guaranteed that that was the only day (unless I was selected for a trial, of course). The problem isn't so much missing a day of work (especially since I own a laptop) but rather not being able to plan anything all week.

Designing a system like this involves balancing a number of variables, so it's hard to back out exactly what the constraints must have been, but I'm guessing it's something like:

  • It's dramatically more inconvenient for people to spend a day waiting in court than it is to not be able to plan their schedule more than 4 business hours in advance.
  • The marginal utility of being in the call-in pool for a week is not much worse than the marginal utility of being in it twice for 2-3 days.
  • It's very bad not to have enough jurors on any given day.

It seems to me that these explain most of the major features of the system, namely that:

  • They have you on call for a week rather than there for a day.
  • That the period is a week rather than having more frequent callups for two days at a time.
  • That they have to make constant adjustments to titrate the number of jurors.

Of course, another explanation is that nobody thought very hard about it and since it's illegal for you not to do what you're told there's not a lot of incentive to think about what's convenient for jurors, so we get whatever system we have.