Around September 20th, all of our site performance data improved substantially. This is the chart that is at Webmaster Tools-> Labs-> Site Performance.
We made no changes at all on any of the sites yet they all showed big improvements of speed. One went down from an average 2.8 seconds to 1.7 seconds. This moved the site from "faster than 57% of sites" to "faster than 76% of sites".
The site also states that "these estimates are of high accuracy (more than 1000 data points)." Previously, they all said "these estimates are of low accuracy (fewer than 100 data points).
The sites are all on different servers located in different parts of the U.S.
Just wondering if anybody else has seen this.