Fun with Calculators

The Sunday NY Times carried an excerpt from Reckless Endangerment: How Outsized Ambition, Greed and Corruption Led to Economic Armageddon, by Gretchen Morgenson. The excerpt is interesting, and the book no doubt equally so. But a calculation slowed my reading:

"According to documents filed in a borrower lawsuit against NovaStar, Aurora Loan Services, a Lehman subsidiary, studied 16 NovaStar loans for quality-control purposes. What the analysis found: more than half of the loans — 56.25 percent, to be exact — raised red flags."

Or, in other words, "nine". The expression "56.25 percent" is most useful in cases where one cannot be exact--election or census returns, say. If you do not trust your readers to remember the previous sentence, the expression could be "nine of the sixteen"; if you do not trust them to remember grade-school math, you could throw in "more than half." But why use two decimal places?

Apparently because calculators make it easy. A couple of years ago, my wife received a synopsis of the student evaluations for a course she had taught. Again, the percentages were carried out to two decimal places. This would have made sense for a lecture section of a few hundred students, but there were 29 in her class. I found myself reckoning Well, OK, that's 23 of 29 thought the homework was appropriate.