That's my point, there is no way to save a story without upvoting it, but the two are mutually exclusive, or atleast should be. People will use the vote button as a way to bookmark stories that they want to read later but are forced to vote as well.
Judging from the comments in this post, I don't think many people knew about the saved stories feature to begin with, and if they do I doubt many upvote a story purely to read it later. There are better services to do that like Instapaper.
Ah, your point is that they may upvote it in order to save it for reading later, but had they read it first, they might not have upvoted it.
Yes, understood. I believe that will not be a significant effect in the analysis I want to perform, but I will keep in in mind.
Thank you.
If I might add a data point, When I am busy, I primarily use the upvote button to read later. It's my instapaper.
I upvote the article based on the content when I am not too busy.