Great Question, Complex Answer. First we have to explain the reasoning behind the question.

It is a fact; search engines view a link to a website as a vote for the site. Now an even better “theory” is that a link from a web site of the same “subject” is a vote that counts more. That’s the Link Quality theory.

If your website is in a specific industry, and another website in the same industry links to you, that is seen as giving better votes for you, compared to a link from a website outside the industry.