Monthly Archives: November 2009

U.S. public debt isn’t that out of whack — yet

People like to worry about the United States federal deficit — when the Republicans are in power the Democrats accuse them of expanding the debt to fund war, and when the Democrats are in power the Republicans accuse them of expanding the debt to fund social programs, and both sides accuse the other of “mortgaging our childrens’ future.” Google has 659,000 hits for that exact phrase. Since the debt passed $10,000,000,000,000 (ten trillion dollars) in 2008, the total debt per person in the United States is about $30,000 — that includes newborn infants and retirees, all saddled with significant debt.

But looking at debt as an absolute number is wrong, as is simply comparing to population. A more relevant number is comparing debt to GDP, to give a sense of how easily the debt could be repaid. In those terms, U.S. public debt doesn’t look all that bad at present. As this list of public debt as a percent of GDP shows, the U.S. isn’t currently that far out of line at 60.8% of GDP — Canada France and Germany all have (slightly) more debt as a percent of their GDP, and many other countries aren’t far behind.

Going forward, however, the outlook is more serious. U.S. debt is projected to hit 101% of GDP by 2011. That’s still lower than it was in 1946, when spending on WWII raised the debt to 109% of GDP, but it’s close, and the debt ratio is projected to be as high as 148% by 2019.

One way out of this is the printing press. The U.S. could simply create a few extra trillion dollars and throw them at the problem. This would roughly double the current money supply, causing the value of the dollar to decrease substantially. Foreign holders of U.S. debt — mainly China and Japan — would be extremely unhappy, but they’re not the main holders of U.S. debt: the Federal Reserve is. How that snake-eating-its-own-tail situation gets solved is a definite puzzle.


No, really: stop me if you’ve heard this one before

Silicon Alley Insider is running an article titled 15 Google Interview Questions That Will Make You Feel Stupid. Several of the questions are interesting, but several are chestnuts that if you know puzzles, you barely remember where you heard them the first time. On the other hand, if you aren’t a puzzle person you’re not likely to solve them quickly and under pressure during a job interview, making them less than useless. It doesn’t help that the article doesn’t display a good understanding of the puzzles, and gets several answers wrong.

Here they are:

Stupid Interview Questions

Continue reading

Stop me if you’ve heard this one before…

New Scientist is running an article about intelligence where they claim that a high IQ doesn’t mean you’re smart. I agree in general, but one example they give is just silly. They cite:

Test your thinking

When researchers put the following three problems to 3400 students in the US, only 17 per cent got all three right. Can you do any better?

1) A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?

2) If it takes five machines 5 minutes to make five widgets, how long would it take 100 machines to make 100 widgets?

3) In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of it?

I can believe that only a small percentage of students got all three right, but I wonder what the researchers thought they proved. The above three questions are the puzzle equivalent of knock-knock jokes: if you are at all interested in word puzzles, you learned these somewhere around the fifth grade.

This reminds me of a job interview I once had, where the interviewer decided to ask me an interview puzzle. I think he started with the doorway choice: you have two doors to choose from, one leading to certain death, and two robots (or brothers, or villagers…) to help you, one of which always tells the truth, one of which always lies. What one question can you ask to make the decision. I told him I already knew the puzzle. So he asked me another, about timing 45 minutes with two ropes that will each burn in an hour. I knew that one as well. So he asked me another. And another. And another. He wouldn’t give up, but he apparently didn’t know any puzzles that I didn’t know. Eventually I asked him if it was alright for me to bring up a puzzle I had recently been working on and describe how I had solved it. He agreed and we moved on. (I got the job)

The problem in both cases is that to anyone who has an interest, the problems aren’t problems at all, and they do nothing to test the individual’s actual ability, but only their level of interest in the field of puzzles and ability to recall old chestnuts; while to anyone who has no interest, obviously they will underperform because they have no interest. If the researchers thought they were testing for intelligence by asking those three tired puzzles, they were sorely mistaken. They were really testing for a general interest in puzzles.

But perhaps an interest in puzzles correlates with intelligence. I’d certainly like to think so 😉

I’m curious how many people reading this were familiar with the above three puzzles.