Match, Don't Mix

   Fractions and percentages don't mix well. Using both in the same sentence forces the reader to translate one or the other to get them to match. Even if the reader chooses not to translate, the inconsistency forces a pause while figuring out what's meant.
   Here's an example, from a CNN Web site: "About three-quarters of Americans are Internet users, compared with about 90% of Sweden's population."
   Hans Auf, our correspondent in Munich, called such a usage "very strange." And while technically not incorrect, "it's less efficient, so why do it?"
   Indeed. It's not efficient, because it slows reading and interferes with communication, so it should not be done.
   The purpose of good writing is to communicate, to transfer information efficiently. Don't put translation barriers in the way. In defense of the mix-and-match usage, some say it forces the reader to think. Perhaps, but it's better that the reader think about the concept, and not spend time on the mechanics of translating or transposing varying sets of numbers to the lowest common denominator. (Some of us haven't dealt with LCD translation since fifth grade, and hated it even then.)
   As for which is better or more efficient, fractions or percentages, the answer is neither and both. Writers should choose the one that most efficiently conveys the message. And once chosen, stay with it.
   So how to choose. If you select percentages, the rule of consistency applies. And in general, it's better to use numerals and decimals in all cases. This is especially true with a range, such as 8.4 to 9.5. Conceivably, you could write eight-point-four to nine-and-a-half, or 8.4 to 9 1/2, but mixing the forms can only jar and distract the reader.
   The goal is communication, not confusion. Unless you're running for political office.