PageSpeed Minification Pecentages Miscalculated

[jaythos]

It looks like PageSpeed is miscalculated the percent reduction for the JS Minify task.

I set up a small web page that loaded jquery 1.10.2 (non-minified) as a test.

Here's the result from WPT:
Minifying http://ajax.googleapis.com/ajax/libs/jqu.../jquery.js could save 38.8KiB (15% reduction) after compression.

Here's the result using the current version of the PageSpeed Chrome extension:
Minifying http://ajax.googleapis.com/ajax/libs/jqu.../jquery.js could save 38.8KiB (50% reduction) after compression.

As a control I hit both the non minified and minified versions hosted on google (gzip compressed) and looked at the sizes via Fiddler:
http://ajax.googleapis.com/ajax/libs/jqu.../jquery.js (Gzip, not-minified): 79.2KiB
http://ajax.googleapis.com/ajax/libs/jqu...ery.min.js (Gzip, minified): 32 KiB
Reduction: 47 KiB (60%)

So the Chrome extension version seems much more accurate, I'm guessing the remaining difference is due to various differences in the gzip and/or minfication algorithms used.


Is this just a matter of updating the PageSpeed version in WPT or am I missing something?

Thanks.