Jeff Bezos is worth a bit more this morning than he was yesterday--and it's just enough to put him ahead of Bill Gates for the title of wealthiest person in the world.

(Of course, to paraphrase Mark Twain, if you don't like who the richest person in the world is, wait a minute.)

In fact, Bloomberg, which keeps track of these things, isn't ready to crown Bezos the world's richest person until trading closes today--which makes sense in way, much as you wouldn't crown the winner of a marathon at mile 13. (On the other hand, it's not like there's a real finish line.)

Forbes keeps its own list, as you probably know, and they're in the same boat as of this moment: tentatively naming Bezos number-1, but also adding that it doesn't quite count until he's been in the number-one spot during their annual roundup. (Forbes says it's named five people the "official" wealthiest billionaire in the past, but one other person held the title for two days.)

Bloomberg explained the numbers thusly:

Shares of the online retailer reached $1,071 in pre-market trading Thursday. If the gains hold, Bezos will take the No. 1 spot from Microsoft Corp. co-founder Bill Gates, who's held the top rank since since May 2013. Amazon shares have risen 40.4 percent this year through Wednesday, and the company reports second-quarter earnings after the market close. Bezos, who owns 17 percent of the company, had a net worth of $89.8 billion as of Wednesday.

It's not quite "paper gains"--people like Bezos and Gates are among the world's greatest entrepreneurs who built some of the most fascinating and successful companies.

But market capitalizations go up and down, or even continue to go up at different rates, obviously, leading to times like the day when Bezos's net worth jumped $2.9 billion in a single trading session. We'll see whether he holds the title for a few moments or for many years. Predictions? Let us know in the comments.