I just don't remember anyone I've known using the same scan rate displays and computers as myself back in the day complaining about flicker or headaches caused by their displays. Were we too young? Don't know.

1/3 of calls could be a pretty low number or percentage of incidents. I don't know how many Nokia monitors were sold nor how many calls you received. But you must have seen offices of hundreds, if not a thousand or more displays all running at 60Hz, no? Besides, 1/3 of calls still puts the number in the minority. Which only helps substantiate my claim of "for most people" - 66% is well into the "most" camp.

Brighter display = longer persistence of image = less perceived flicker. At least that's what I've always learned. Other strains are caused by looking at a dim display. Try it yourself. I can adjust display brightness at my fingertips, and a dim display gives me eye strain very quickly. This has nothing to do with flicker of course, which is what I was saying initially.