Wednesday, November 16, 2005

Doing the Math

Yesterday's Washington Post carried an article on a study which showed that working out could improve your life expectancy. Essentially, the study claims that if you walk for half an hour a day, your life span will go up by nearly 1.5 years. More strenuous exercise produces even more benefits (up to almost 4 years).

Of course, I immediately had to figure out whether it was worth it. Sure, you live a little longer, but if you have to spend time exercising every day, is there a net gain? That is, does the total amount of time spent exercising exceed the increase in life expectancy? A quick calculation showed that there is a substantial benefit; depending on the amount of exercise you do, the total time invested is only between 1 and 6 months. (Admit it, you were disappointed. You were hoping for an excuse not to exercise - ed.)

Anyway, I'm bringing this up because I thought at the time that the article could have been strengthened by including this information. It would have been intellectually honest to point out that the 'net' increase in life span was a little less than claimed (especially when they claimed precision by using figures like 1.7 years), it would have saved geeks like me from performing the necessary computation, and most important, it would have helped readers relate to this kind of simple cost-benefit analysis. I put the omission down to the general math-phobia in the media, imagining some assistant-deputy-sub-editor removing it on the grounds that the math would drive readers away from the article.

I was surprised and delighted, then, to find an editorial - no less - in today's Post with all the omitted math - and then some. It adjusts the time spent exercising depending on how it affects the rest of your day and makes allowances for sleep (something I forgot to do!). Best of all, it includes the compound interest idea! That is, it assumes that time now is worth more than later, and allowing for the possibility of accidents, etc., it discounts the future at a (compounded) rate of 3% per year.

Unfortunately, even after making all the allowances one can, there's still an overall benefit. I guess that means I no longer have a good reason not to exercise.

3 comments:

Sanketh said...

Haven't you heard of the bird flu old man? Doesn't it figure somewhere? To keep that at bay some one has to eat all those chickens. If I exercise I'll be less motivated to eat (you know so that I don't get back all that I have lost). So you've got to include that in your cost benifit analysis. Do all that and it'll show exercising isn't getting you anywhere.

Nitish said...

Nice try, Sanketh, but it's not going to work. I'll start exercising... after my quals, next year.

Of course, in the meantime, I intend to attack a 1000-calorie DQ Blizzard after dinner.

Arun said...

"I guess that means I no longer have a good reason not to exercise."

Hehe. Of course there is. In fact, there are infintely many reasons.:)