Trying to id a sci-fi short story w/ alternate universes

I’m trying to id a particular SF short story I read in some compilation a few years ago. The problem is that I have a very foggy rememberance of it. In fact, I only remember the basic premise (I think). It was something about how our perceived reality is the sum of all the possible alternate universes. That all the branches happen and exist out there, and that they get merged together and form “reality”. There was also some bit about how a given person never dies, since reality from their perspective only consists of the alternate universes where they are still alive. I thought it was a pretty neat concept and would like to re-read it, but can’t find it at all.

I know I’ve done a horrible job of explaining this, but does anyone have a clue what I’m talking about?

It could be any of of many stories that deal with the concept, but I’m guessing it’s Larry Niven’s “All the Myriad Ways.”

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I thought “All the Myriad Ways” involved the discovery of alternate timelines and a method of travelling between them. People started committing crimes that made no sense because they realized that in some other timeline those crimes wouldn’t be committed, so they felt it didn’t make any difference what they did, and in once case a man killed himself to “save” alternate versions of himself.

Could the story be Divided by Infinity, by Robert Charles Wilson? I just read that in the 1999 Year’s Best Science Fiction. Here’s a quote from the very end:

The man in the story reads a book about the multiple universe theory, and how we never really die, but live on in another reality. He continues living for a very long time, as he becomes increasingly unlikely, but he carries his awareness through all the different universe. Eventually, he is the last human in the world, cared for by a strange race of aliens who keep him alive to learn what the Earth was like.

Yes yes yes! I’m almost certain that’s it, because I have that volume (along with about 10 other ones from that series). Vanyel, thank you so much! I’ll have to go home and read it again.

No problem, I just read it a couple weeks ago. In fact, I’m still working my way through that book.