November 21, 2008
There’s a disease that has befallen the Western world. I call it percentitis. The syndrome is quite simple: Every relation, ratio, growth or decrease of some sort is quantified in percent. I think it’s unnecessary, even misleading sometimes, and just a futile attempt by the marketing drones at making boring things sound interesting. After all, “I agree 100%” is just another way of saying “I agree completely” and “I got this blender for 50% off” isn’t really that much better than “I got this blender for half the price.”
You might be right in saying that’s nitpicking. However, by far the biggest beef that I have with percent is when it’s used for quantifying an increase or decrease:
BigCorp has grown continually by 7% each year for the past four years.
Compare and constrast this with
BigCorp has grown continually by factor 1.07 each year for the past four years.
I know it sounds weird because we’re not used to saying it like that. But these incremental percentages would be just as weird to somebody who’s never heard of them. After all, they’re specifying what’s essentially a factor in
(x-1)*100%. Indeed the percentage form drops an in my mind important information, the
1. I know it’s implied. I know that everybody should’ve learned this in 8th grade math. But why do we deliberately obscure the fact that it belongs there? For instance, imagine that you’d like to calculate the overall percentage by which BigCorp has grown over the total of four years. It’s
((1+p)^4 - 1)*100% where
p is the percentage. Compare and contrast this with
q is the factor in the second statement. The result for this example is 1.31 or 31%, by the way, and not 4*7% = 28%, as somebody might naively think. Again, people should know the difference, but maybe they don’t. If we actually used the factor form, they might not be fooled in the first place.
Percentages might still be useful when talking about fractions, but then again, I don’t get why we don’t say 0.57 instead of 57%. It’s not really shorter or any easier to understand. I suppose it’s the same reason why we say 1000 km instead of 1 Mm (that’s a megametre): convention. So there we are. Percent: it’s absolutely useless. Don’t need it and don’t want it.