Exact numbers corrected 10 November 2014.
How many ATA-certified translators are there? I couldn’t find a quick-and-easy answer to this question, so I went and did a little digging in the directory. (Or rather, I used a Python script to dig through the downloaded data for me.)
The upshot: At this writing, there are 1,679 ATA-certified translators in the ATA directory. These translators hold a total of 1,991 certifications in 29 language pairs. (Note that that’s a larger number of language pairs than the ATA currently offers certification in, since some pairs like Finnish-English and Italian-English are no longer offered).
The great majority of these certified translators (1,435, or about 85%) are certified in only one language pair.
198 of them hold exactly two certifications. Of those, 141 (just over 70%) are “symmetrical” — for example, Dutch-English and English-Dutch.
29 translators (including me) are ATA-certified in three language pairs. 12 are ATA-certified in four language pairs.
At the top of the heap, exactly five translators are ATA-certified in five language pairs. At this writing, nobody has more than five certifications.
Interestingly, of that elite group of five, only one has even one ATA certification that is not into English. This confirms a distinction I’ve noticed informally. There are some truly bi-fluent bi-directional translators, and there are some who translate from multiple languages into English (or another language like Korean)—but there’s very little crossover between these two groups.
I suspect that a closer inquiry might show that these groups approach the translation process in very different ways.