The theory is that a link from an .edu or .gov website to another website is considered more authoritative by search engines such as Google, and would thus boost the site with the incoming link in the rankings.
It doesn't make sense to me. But enough webmasters have said that it does that I'm trying to figure out how to measure the effect.
The link would have to be to a site that's almost an unknown. One that's in the search engines' indexes, but isn't going through the daily fluctuations that the top-ranking sites do.
I'm sure that there's at least one THR member who has a low-ranking site that would be appropriate for this experiment.
Please let me know if you have the authority to add a link from your site.