Our site is aimed directly at UK visitors as they are the people we sell to. We host in the UK and have a .co.uk domain.
Signing into Google's Webmaster Console I am concerned about the performance Google is reporting. Google is saying our website is slow. That is a bit of a problem given that they are, or will, roll the performance data into their ranking algorithm.
The performance I get is nothing even close to the slowest load times they report (13-14 seconds). I have asked somebody else in the UK to load the site and they report in the region of 1-2 seconds per page.
I am concerned about the disparity between the reports I am getting and what Google is reporting. Ordinarily I wouldn't be too concerned but Google will be using their performance data not mine.
Are google measuring site performance data solely from California or are they measuring from where target visitors will be visiting from? Optimising my site for visitors from California doesn't make much sense for me.
Google is aggregating user experience from browsers that have the Google toolbar installed and PageRank activated, so it's not confined to California-based data at all.
This performance metric is a new feature and it's not all that accurate yet. You bring up an issue that may not even be folded into the calculations, yet - namely that if a site is targeting a specific country in their WMT settings, then performance data should be at least weighted to those users.
There are some lively threads in Google's forums about a similar situation. For example, one member says [google.com] he worked hard to get his pages down to 1-2 seconds but the WMT report is showing 83 seconds for all but two urls.
In a burst of refreshing candor, a Google employee named sreeram (he gets involved in a lot of the site speed threads) replied "the 83s number is bogus" and explains many issues that can come up. From Sreeram's many forum comments, I'm assuming that site performance is not yet nearly ready to be rolled into Google's ranking algorithm.