Furthermore, users do fewer and fewer searches the longer they are exposed to the experiment. Users exposed to a 200 ms delay since the beginning of the experiment did 0.22% fewer searches during the first three weeks, but 0.36% fewer searches during the second three weeks. Similarly, users exposed to a 400 ms delay since the beginning of the experiment did 0.44% fewer searches during the first three weeks, but 0.76% fewer searches during the second three weeks. Even if the page returns to the faster state, users who saw the longer delay take time to return to their previous usage level. Users exposed to the 400 ms delay for six weeks did 0.21% fewer searches on average during the five week period after we stopped injecting the delay.
While these numbers may seem small, a daily impact of 0.5% is of real consequence at the scale of Google web search, or indeed at the scale of most Internet sites. Because the cost of slower performance increases over time and persists, we encourage site designers to think twice about adding a feature that hurts performance if the benefit of the feature is unproven.
One of Google's earliest advantages in the search market came from speed and they've never dropped the ball. The home page and their search results load extremely fast and their success even pushed the other majors to de-clutter their overstuffed home pages.
I appreciate that they published their research results very much.