How much do online readers read?

Usability expert Jakob Nielsen, projecting from a new German study, suggests that most users read about 20 percent of the words on a Web page and at most 28 percent.

Nielsen's calculations rely on a formula he derived from the study's dataset. The formula suggests users spend 25 seconds plus an additional 4.4 seconds per 100 words on a page. Nielsen's result is that -- assuming a fairly fast reading speed of 250 words per minute -- you have to have fewer than 111 words on a page for half of them to be read.

As he says, the curve declines precipitously from there.

Interesting reading, given the Poynter Eyetrack study of last year that suggested that once an online user chose to read a story, he or she finished much of it, even for a longish 19-inch story (still 62 percent).

However, the two studies might not conflict. The German study used software that intercepted pages and other behavioral data. Poynter used eyetrack, which physically tracks how far a person physically goes into a page, but does not track how many words each is actually reading..

Given the wide acceptance that most Internet users are scanners, it's possible they were reading few actual words even though they were going deep into a story. We would need time data from Poynter to determine that.

Bottom line is that while we keep studying it, we really don't have a truly solid handle on user behavior, partly because of the changing nature of the web.