I am a firm believer that in every project, we should forget about small inefficiencies, say about 97% of the time. “Premature optimization is the root of all evil” said Tony Hoare. However, while doing some research on how a long loading time affected user drop-off rates, I found this great post by Alex MacCaw on Asynchronous UIs.
It shows you how perceived speed matters to your users and how it can affect your engagement and hence, revenue. Great UI design is important but we should always keep in mind that the ultimate goal of a UI is not just to be seen, but to be actually used.
Here are a few facts :
Amazon: 100 ms of extra load time caused a 1% drop in sales (source: Greg Linden, Amazon).
Google: 500 ms of extra load time caused 20% fewer searches (source: Marissa Mayer, Google).
Yahoo!: 400 ms of extra load time caused a 5–9% increase in the number of people who clicked “back” before the page even loaded (source: Nicole Sullivan, Yahoo!).
Premature scaling may be the root of all evil but we should have these stats in mind when developing applications. Especially in this day and age when people are flooded with mobile apps, web apps, email, checking twitter or their FaceBook account, the user’s attention is more than ever harder to get.