Isn't "not" upvoting same as "downvoting"? I mean on HN the frequency of people who click on a link, if not at all worth would be less than 50-60. Not sure ho

Isn't "not" upvoting same as "downvoting"? I mean on HN the frequency of people who click on a link, if not at all worth would be less than 50-60. Not sure how the HN algorithm works but am pretty sure it does well.