1script - 7:27 pm on Feb 10, 2013 (gmt 0)

Clinking on links shouldn't give any credit to the site if time on each page isn't long enough.

"Manufacturing" this user experience metric is incredibly easy: make the next page as cumbersome and convoluted as the previous one and put anything that resembles a link to the resource the visitor is looking for at the very bottom (or below the fold, anyway). That'll get you a second a two extra to fool any automated filter. A human being would have spotted this instantly but Google never had and never will have enough human beings to check on everything. Besides, some of the landing pages are (or purport themselves to be) about very complex subject in which you actually have to have some kind of understanding to realize that you are being fooled.

@Simsi: regarding the vague context of the original search term that may be playing a role in this. In my niche the most blatant offenders are sites that contain collections of datasheets on various parts and devices. The initial queries are very simple and cannot even be taken two ways: when you type "blue widget datasheet", I guarantee you 99% of the time you want to download PDF that contain the said datasheet.

What happens next is very indicative of the user metric abuse going on, as described in this thread. Many of the datasheets are not so easily available and pretty much noone has them - the manufacturer probably never made them available online. The more rare the datasheet, the more determined the searcher to find it and so you can have at least two or three pages where you will have lists of OTHER datasheets, sometimes related, sometimes not, and on the bottom you'd see a link saying something like "see other blue widget datasheets". Since you haven't gotten what you came for yet, you'd click there thinking their sorting is off and the one that you need is surely not far away, but no such luck. I can imagine some people looking for information on rare parts, could click much more than 2-3 pages, simply out of desperation.
So, there you have it: the bounce rate goes down simply by definition - they are still on the site. Number of pages opened is high and time on page is usually still decent - they are normally filled with pretty long lists of complicated part numbers - you will need at least several seconds to realize that what you are looking for is not there, and several seconds is a VERY decent on-page time by today's standards.