A couple of years ago Google introduced Site Speed to it's search algorithm. This is a measure of how long it takes a page to load. You can track this measure for your site in Google Analytics as well in Google Webmaster tools.
Recently I've been investigating this measure for some of our sites and was quite surprised at how long Google thinks it takes our pages to load. Page load times as measured by Google were several seconds above the one second it takes for our largely static pages to load from the end users perspective. I measured this from several remote locations on different continents and our pages appear to load in about a second. Crucially the time measured by Google is also above their recommended maximum page load time. Why the difference?