Mobify (2016): For every 100ms decrease in homepage load speed, Mobify's customer base saw a 1.11% lift in session based conversion, amounting to an average annual revenue increase of $376,789. Similarly, for every 100ms decrease in checkout page load speed, Mobify's customers saw a 1.55% life in session based conversion, amounting to an average annual revenue increase of $526,147 [2].
Staples (2014): conversion increase per second [3].
Or the Obama campaign (2012): making the page 60% faster increased donations by 14% [4].
More new studies from recent years can be found at WPO stats [5].
[1] https://www.doubleclickbygoogle.com/articles/mobile-speed-ma...
[2] http://resources.mobify.com/2016-Q2-mobile-insights-benchmar...
[3] http://de.slideshare.net/cliffcrocker/velocity-ny-how-to-mea...
[4] http://kylerush.net/blog/meet-the-obama-campaigns-250-millio...