Obvious Diversion

Boingboing has a story up about Bedford’s Law that’s pretty cool, but the math used in the examples has a couple blatant errors in it. I’m not questioning the validity of Bedford’s Law, but simply pointing out a couple problems with the examples that were chosen to demonstrate it which were originally taken from this New York Times article.

“To get to a Dow Jones average with a first digit of 2, the average must increase to 2,000, and getting from 1,000 to 2,000 is a 100 percent increase.

“Let’s say that the Dow goes up at a rate of about 20 percent a year. That means that it would take five years to get from 1 to 2 as a first digit.

Actually, it only takes four years. At a rate of 20 percent a year, by year four the Dow would be 2073.6

“When the Dow reaches 9,000, it takes only an 11 percent increase and just seven months to reach the 10,000 mark, which starts with the number 1.”

An 11 percent increase doesn’t get the Dow to 10,000. An 11 percent increase of 9000 is 9990, not 10000 or more as the quote states.