So I was recently involved in some performance tuning for a fairly large Australian website. One of the problems with performance tuning is that typically there’s no historical metrics to compare any changes against.
Fortunately, Google records this infomation as part of their crawl, and if you have signed to use the Google Webmaster Tools you can see this data.
In our case, this was very useful, because we were able to demonstrate a pretty significant improvement (download time (ms) vs Date):
(year, I know – I’m still not really happy with that performance either, but there are some infrastructure problems which are proving difficult to work around….)