Many SEO professionals spend a large amount of racing against the Google Pagespeed clock to win favor on Google. Does it work? Is this speed even accurate? and why many successful sites don’t seem to care?
Big sites like adobe.com ranks in the red and amazon.com(39) is only little better. But both of those sites seem perfectly usable loading speed. In fact sometimes the opposite is true. NBC news with high GPI ranking but very slow load time and Amazon with record quick (1 sec) load speed but a bad score. To see more details and a graph look at this article from AbsentData.
Google PageSpeed Insights (GPI) does not measure the page loading time. The key is Insights, GPI analyzes the content of a web page, then generates suggestions to make that page faster. If you want to measure the actual page load speed use a tool like pingdom or webpagetest.
Does it give favor in the Google ranking algorithm?
Google has repeatedly announced that a good user experience plays a huge roll in search ranking. Since this is their main tool for measuring speed then it looks very important.