Knowledge wants to be free !

We have decided to give away world-class educational materials because we believe that universal access to high quality education is key to the building of peace, sustainable social and economic development, and intercultural dialogue.

To calculate just have much we have saved you, our wonderful readers, we compare our free encyclopedia to two books we love:

$110: Human-Computer Interaction by Dix et al (a great textbook but without video interviews)
$116: Shneiderman's Designing the User Interface (a great textbook but without video interviews).

As you are reading our encyclopedia on your iPad/tablet (and saving a few trees), we estimate that the price would be $90 if sold as an eBook. With that number, we can calculate how much money we have saved our readers, based on calculating the number of readers.

How we calculate readership

Because of our online and tablet/iPad approach to publishing, we are able to precisely measure reading behaviour across hundreds of parameters in realtime: Anything from reading speed, drop-off points in the text, reader demographics, and much more.

Based on our server logs and the Google Analytics API, we calculate the number of readers as described in the calculation method below. A reader is not the same as a simple pageview and a reader is not the same as a website visitor (as described in our calculation method below). We calculate readership for two types of readers:

1. Readers that have read our whole encyclopedia, much the same way you read a printed book
2. Readers that have reader an individual chapter

Calcalution method: How we define a reader

1. First we use the Google Analytics API to get a report of the number of unique human visitors to a chapter/page. Google runs its business on ads and thus completely relies on the ability to distinguish between a human visitor and an automated request. If not, you could earn millions on automating clicks on Google Ads.
2. We then compare that number to our Apache webserver logs, which report the much higher number of actual visits to a chapter/page (both human and automated). We calculate the difference in percent, which we call an "exaggeration factor", which we use in step 6 below.
3. With a large part of the visitors excluded, we further exclude any visitor who:
   1. has not remained on the page for at least 3 minutes (this factor is calculated by recording visit durations of 1000 randomly selected visitors) or has not printed the page (i.e. has not visited the printerfriendly version of the chapter/page)
   2. has not scrolled the page (this factor is calculated by recording scroll movements on 1000 randomly selected visitors)
4. We then further exclude "double readers", i.e. readers who read a portion of a chapter and then returns in, say, a week or a month to read the rest. Although this person's reading activity spans multiple server sessions, the person is only counted as a single reader. We categorize a "double reader" as a visitor who:
   1. visits a page, or multiple pages, across multiple server sessions
   2. qualifies to be defined as a reader, cf step 1-3 above, in all server sessions
   3. uses the same originating IP address
5. We then subtract 5% from the final number to counter-balance a last remaining factor, namely the situation where one reader reads a chapter on his/her tablet using a WiFi connection (and counted as one reader) but then picks up his other tablet using a 3G dongle (with another IP address) and re-reads some of the chapter. That will equal two readers, not one. We have no way of calculating how many times this situation arises, but to be on the safe side we subtract 5% from the final number.
6. We then take half of the "exaggeration factor" from step 2 and substract from the final number. We do this for no rational reason. We do it only as a further measure to be certain that our number of readers is not inflated.
7. To qualify as a reader who has read our whole encyclopedia - much the same way you read a printed book - that person must have qualified as a reader (cf. 1-6 above) of at least 80% of the encyclopedia chapters.

As a result, we have eliminated everything from automated requests to the more casual visitors. That leaves us with what we can safely call readers.