I just read a dissertation on how (supposedly) page rank works. According to what I read, the more outbound links that you have to other sites, the more it lowers your page rank. Is that true in general? I mostly cite authoritative sites like webmd, sciencedaily, etc. In fact, I read one post where a reader said that he put in all the links for the studies that he was using and it boosted him in the search results. So I am wondering where the truth lies? Is it good/bad for your page rank/search engine rankings to have a lot of outbound links to other sites?
This is pretty much false, although there is a TINY bit of truth to the statement. Let me try to explain... A given URL's PageRank is determined by its INBOUND links, and has ALMOST nothing to do with it's outbound links. I say "almost" because by linking to external sites, you reduce the amount of PR you can recirculate around your own site. For example, say your page has 100 outbound links on it with all 100 of the links pointing to internal pages on your own site. If that page has 500 PR points then approximately 500/100 or 5 PR points will be passed out on each of the 100 links that are followed (there is a damping factor or decay factor that slightly reduces the amount of PR passed out to about 85% of the total PR of the page - why I said "approximately"). Since those points are being passed to other pages on your site it helps them increase their PR... and therefore increases the amount of PR they can pass out on their outbound links. All of the PR from that page gets recirculated around the site... Now imagine the exact same page with 100 outbound links, but now the page has 20 links to external URLs and only 80 links to internal sites. If the page has 500 PR pts then approximately 5 PR points will still be passed out on each of the 100 followed links, but NOW about 100 of those points get passed out to other sites, and only about 400 points (instead of 500 points) get recirculated around your own site. But this example is VERY extreme IMO. It is rare that 20% of the links on a page point to other sites. Most pages on web sites have between 50 and a couple hundred links per page. So linking out to a few external sites per page is NOT going to make a drastic difference in the the amount of PR that is "lost" to other sites. The more correct statement would be that the more outbound links on a page, the less PR that is passed out on each of those links (regardless of whether they are internal or external URLs that you link to). Linking to authoritative, trusted sites can help to increase your site's domain trust which is a ranking factor at least at Google. So it "can" help your site's rankings to link out to other sites... although I would be willing to bet that 1) inbound links FROM other trusted sites carry way more weight than outbound links TO trusted sites and 2) the affects of increasing domain trust are only noticable when a site becomes highly trusted. It's HIGHLY unlikely that adding a few links to authority sites noticeably boosted their URL's rankings. I would NEVER hesitate to link to other sites if you are citing them as an authority on some particular topic you are writing about or if the site is related to your content and you feel your site's visitors would benefit. However, I would make sure that you TRUST the sites you are linking to and are willing to put your site's reputation on the line. Otherwise, you should NOFOLLOW the link. If you link to a bad neighborhood site with a followed link then your site can be penalized for promoting a bad neighborhood site.
Wow! Thx so much for all the explanation. Question: why do sites NOFOLLOW their comments so often then?
Because they do not trust the sites they are linking to, and not not willing to put their reputation on the line.
Pagerank is google link analysis algorithm, which founded by the Larry Page and Serge bin (founder of Google) which given numerical weight to website based on the hyperlinks each of the web.Outbound links are a drain on a site's total PageRank. They leak PageRank. To counter the drain, try to ensure that the links are reciprocated. Because of the PageRank of the pages at each end of an external link, and the number of links out from those pages, reciprocal links can gain or lose PageRank. You need to take care when choosing where to exchange links. Obviously it is bad if you have more outbound link than inbound links of other sites.