Faster sites mean more money.

By | August 6, 2007

Google found that when pages took only half a second longer to appear, usage of their site dropped 25%.  In her talk, Scaling Google for Every User at the Seattle Conference on Scalability, Marissa Mayer communicated these results. The explanation of the statistic starts around 9 minutes into the video and takes about 3 minutes.

http://video.google.com/videoplay?docid=-7039469220993285507

Also, Amazon found every 100ms of latency cost them 1% in sales and Wikia found that faster pages reduces exit rate.