I'm periodically asked: what percent of today's new hearing aids come with telecoils (which receive magnetic input from hearing aid compatible phones and from hearing loops). A decade ago, 30 percent was the common estimate. Recently, two annual surveys of hearing professionals reported by the Hearing Journal (see Figure 4 here and here) have both reported 62 percent. This increase is thanks partly to the surge in behind-the-ear (BTE) aids, most of which come with telecoils (though, sadly, not yet all the new mini-BTE aids). People with significant hearing loss and need for hearing assistance mostly wear BTE aids, which explains why 84 percent of Hearing Loss Association of America members in one survey reported having telecoils.
The March/April 2009 Hearing Review Products offered a technology guide to in-the-ear (ITE) hearing aids marketed by a dozen companies (Audifon, Audina, Bernafon, Oticon, Phonak, ReSound, Siemens, Sonic Innovations, Starkey, Unitron, Widex, and Rexton). Voila!, all 35 ITE models--100%--are now coming with telecoils. Ditto, it seems, for today's modern cochlear implants.
Happily, hearing loops can serve 100 percent of people, including those without telecoils or even without hearing aids. That's because all assistive listening systems come with portable receiver/headsets (though very few folks, at the point of their need, will take the initiative to get up, locate, wear, and return such).
(Note: Photo courtesy Tibbetts, now Global Coils.)