You're doing it wrong.
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Generally, there's an "other way". The answers to this question are all great, but honestly, you should look at a different option. Squeezing as much text in as little space as possible **always** means you've botched a previous design choice.

- Perhaps you should have flipped them to be horizontal bars, giving you WAY more space to work with.
- Perhaps you shouldn't have gone with a bar chart, or shouldn't have gone with charts in the first place.
- Perhaps the problem is the actual data, and you might've had to split it up even further!

There are so many options, make sure you use the right one. Squeezing as much information into a single small area as possible is *always* the wrong way to go. Information needs space to breathe, to be readable, to be scannable and recognizable.

Yes, this generally means using way more space. But that's not a bad thing. It will take less effort for the person who consumes the data to quickly scan a couple of pages filled with well-structured information, than to figure out what that one bar means on that one-page-report. Think of the old board member, pocketing his reading glasses while passing the paper to the person next to him: "I can't read this - what does it say?"

*Apologies for the harshness and slight tongue-in-cheek title, but I see that top answer and just feel that this had to be said.*