Folding times: a too-rare editorial post

[blatherskite]

As a science editor, I do a lot of number wrangling, since scientists, economists, and other professional writers are surprisingly bad at mathematics. Sometimes they're just sloppy or lazy, sometimes they pulled numbers from the wrong row or column of a big table or misread a graph, sometimes they're presenting detailed calculations from a spreadsheet but using heavily rounded numbers in the actual manuscript (so the numbers don't add up), and sometimes they've actually misunderstood their own equations. (Yes, the latter one actually happens every now and again.) I never assume my authors got the math right, since often they didn't, and one or two simple calculation errors can undermine the reader's faith in the rest of the manuscript.

Sometimes the math is correct but the wording is unclear. One of the most common problems is using "times greater/lower" or "twofold increase/decrease". In both of these pairs, the problem is the same:

Times or fold higher is unclear because it has two possible meanings in English: First and most often, it just means "times". So if an author writes "X increased twofold", they usually mean that X increased to 2X (i.e., it doubled). Second and less commonly, they actually mean a simple numerical increase. For example, 2 is one times higher than 1: you start with the 1, then add 1 one more time.

Times or fold lower is undefined in English: it has no meaning either in words or in mathematics. The usual meaning of "the final value was 2 times lower than the original value" is that X decreased to X/2 (i.e., to half its original value).

In most cases, you can calculate the change using the actual data the author used to perform the calculation; it's usually presented somewhere obvious, such as in a table or figure, or even stated directly somewhere in the text (usually in the Results section). The simplest solution in all cases is to revise the sentence to say "X increased/decreased to Y times the original value". This is always clear, never equivocal, and does the reader a kindness by doing the math for them instead of making them check the calculations.

When you can't do this simple check (e.g., when the calculation is based on the results of a complicated equation you don't have time or expertise to work through), frame a simply query that explains the problem, proposes your best bet at a solution, then offers a second solution if the first one isn't correct. For example:
"My calculations show that the final value increased to 2.77 times the original value. If that calculation is correct, the sentence should change to "... increased to 2.77 the original value". If not, please send me an explanation so we can choose the correct wording."

The inspiration for this post came from a colleague's question. Feel free to submit your own editorial questions, and time permitting, I'll blog the answer. (Send e-mail to ask me to start a new topic if the question isn't directly related to the current posting.)