The Economist December 1st 2007 - Online Public Access Catalog

Web metricsMany ways to skin a catNov 29th 2007 | SAN FRANCISCOFrom The Economist print editionSuch a lot of data, so little informationIMAGINE you are an advertiser, you want to place your banners on the most popular website, and you want to know how much to pay. Globally, theleading site is Google, which has the most “page views”. Or is it Microsoft, whose various sites have, in the jargon, the most “time spent”? Or shouldyou go by unique users, duration, hits, click-through, impressions, queries, sessions, streams, or engagement? Whether or not there is truth inadvertising, there is certainly none for online advertisers, at least none that is immediately obvious and simple. Bob Ivins, who is in charge of allnon-American business for comScore, a big web-measurement firm, says that the web produces data as “a fire-hose shoots water”, and that workingout what those data mean is rather like “putting a straw into the fire hose to take a sip”. Get the angle even slightly wrong, and you are blown away.Take, for instance, the case of page views, the most widely used measure for much of the past decade. It is the number of times web surfers call upweb pages on a given site. Page views became popular in the late 1990s, because they were far superior to the existing measure of “hits”, alsoknown as “file requests”. Hits are confusing because every graphic on a page, as well as the page itself, counts as a hit. If a site owner puts moregraphics on his pages, he gets more hits, even if visitors, clicks and everything else stay the same. “We produced hits numbers because we could,not because it was useful,” says one old-timer in the industry.By comparison, page views do actually mean something, and are easy to comprehend by analogy to the offline world to boot—many advertisers arestill used to counting pagination in magazines. So everybody started paying attention to page views. But then something odd happened. Page viewsat certain kinds of websites, especially the more sophisticated sort, began to decline, even though the site appeared otherwise healthy and popular.The explanation has to do with “Web 2.0”, and more specifically with a constituent technology called “asynchronous JavaScript and XML”, or AJAX.This is a method that lets web pages update parts of themselves—a share-price ticker or an e-mail inbox, say—without having to reload and redrawthe rest of the page, resulting in web pages that behave less like documents and more like pieces of software. But this means that a user of an AJAXpage, such as Yahoo! Mail or Yahoo! Finance, can spend the entire day working on the same page, and this activity counts as only a single pageview.Perhaps advertisers should therefore ditch page views in favour of “user sessions”, since that promises to count actual people, and show how manyof them use a site. Except that it doesn't, because this measure counts browsers rather than humans. So 2m sessions could mean, theoretically, that2m people visited a site once, that 1m people visited twice, or that one astonishing individual visited 2m times. People tend to check their favouritepages in the office, at home, and even from their mobile phones, which leads to an overestimate of the number of users. Conversely, sometimesseveral people watch YouTube clips when gathered around the same screen, which leads to an underestimate of the number of users. Nobodylooking at user sessions would ever know.As websites, and especially those using AJAX, become more interactive, advertisers are therefore interested in other measures. “Duration” and “timespent”, for instance, suggest how long one or more people were interacting with a page, which in turn hints at how “engaged”, or alert, they were.Using these criteria, social-networking sites such as Facebook and MySpace (part of Fox Interactive Media in the chart) suddenly look attractive.In the old days of traditional media, measures may have been simpler, but they were also dumber, says Randall Rothenberg, the boss of theInteractive Advertising Bureau, a trade association. In broadcast television or radio, firms such as Nielsen or Arbitron traditionally give gadgets tosamples of volunteers that measure what their televisions or radios are tuned to; or they ask people to fill out diaries describing their reading,listening and viewing habits. Both methods produce notoriously unreliable estimates.The web is an open book compared with those old media. Search advertisements, the text links on the results pages of search engines, chargeadvertisers only when a user actually clicks, thus expressing an interest. “Pre-roll” advertisements that run at the start of a web video report backexactly how many times they were viewed. But when it comes to banner advertising, says Mr Rothenberg, advertisers just have to consider all thesenew measures as they would a pointillist painting by George Seurat: looking at one dot is no fun; taking them all in can be rewarding.Copyright © 2007 The Economist Newspaper and The Economist Group. All rights reserved.