A study has been carried out which proves what many (including myself) in the SEO field have long believed, but has never been proved... That outbound links to authoritative websites in your content improve your ranking.
There are various myths and fables within the online marketing community. The vast majority of which are unsubstantiated, untested and unproven. However, a recognised and commonly observed fact is that incoming links can have a positive, as well as negative effect on your website’s authority and in turn its ranking. What is less obvious and less tested is the effect that outgoing links can have.