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Chapter 1. Response Time: Eight Seconds,... > Bailout Rates and Attention Threshol...

Bailout Rates and Attention Thresholds

The bailout rate is the percentage of users who leave a page before it loads and start looking for a faster, more engaging site. In their first “Need for Speed” study of 1999, Zona Research found that pages larger than 40K had bailout rates of 30 percent.[29] Once the designer reduced the same page to 34K, the bailout rate fell to between 6 and 8 percent, a dramatic decrease for just a few kilobytes. When fat pages were reduced to the recommended maximum of 34K, readership went up 25 percent.[30] These are averages, and users with faster connections and processors will experience faster downloads, but they can also become frustrated.

[29] Zona Research, “The Economic Impacts of Unacceptable Web-Site Download Speeds,” Zona Market Bulletin [online], (Redwood City, CA: Zona Research, 1999 [cited 9 November 2002]), available from the Internet at http://www.keynote.com/solutions/assets/applets/wp_downloadspeed.pdf. The oft-quoted “Need for Speed I.”

[30] Jacob Nielsen, Designing Web Usability, 49.

Zona's second study, “Need for Speed II,” took into account dynamic transactions in order to modify the so-called “8-second rule.”[31] They recommend that designers of dynamic sites cut an additional 0.5 to 1.5 seconds off connection latency in order to stay at the same level of abandonment compared with static web pages. As the web moves from a “plumbing” (pipes delivering pages) to a “transaction” (a series of dynamically generated pages) model, they argue that “cumulative frustration” plays an important role in user satisfaction.

[31] Zona Research, “The Need for Speed II” [online], 2001.


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