exercise in future web traffic prediction last month must have caused some interest among its target audience, because I've been asked for more. This time with a twist.
The question: "If we add a load of extra pages to a web site, what effect will that have on the traffic?". How long was that piece of string again?
An impossible question to answer. It depends on factors too numerous to quantify and any figures I come up with can't be trusted, I said. We know, they said, but give it a go anyway.
So I thought about it and decided on the well-known theoretical model of a long tail web site. One with many pages, each of which scores on its own search term and each of which only brings in a few visitors, but when all are taken together the total of all the visits for the site is a very large number. In a long tail site, visits are proportional to page numbers, so all I had to do was work out the average number of visits per existing page and multiply that by the number of new pages for an estimate of the extra traffic.
My problem was that the figure I reached looked far too optimistic. Believable I guess, but only just. An upper error margin for my new traffic estimate.
And there lies the fatal flaw in web traffic prediction. As I remarked last time, all I am doing as I go further into the future is giving myself an ever-increasing error bar on my figures. And by adding yet another estimate on top of an existing estimate, all I am doing is increasing that error bar to the point at which the figure becomes meaningless.
Still, it's an interesting exercise, if only to create some pretty graphs.