In css, it would be
another CSS option is to ensure your cols are wide enough that no browser would consider wrapping the numbers.
However, it's the number "negative thirty-four percent" right? So it makes sense to do this in HTML (if there were no CSS, you still need -34% don't you?).
Unfortunately the only tag I can think of is the nobr tag, which should get flagged as invalid as it's not recognised by the w3c.
Some browsers will break at a - while others don't. Possibly a better way is to manually code in the correct character (the - button on your keyboard is a sort of "everything but mostly minus and hyphen" key). Technically a minus used for negative numbers is a hair longer than a hyphen.
& # 8722; without spaces is the code you would have in your HTML. I do not know if the browsers who wrap at a - will wrap on that.
One issue with using a character like that is, possibly some web fonts (even popular ones) won't recognise that character and may add a box or ? in place of it.. test it and see. Minus should be pretty popular though, but I ran into trouble when using the hyphen bullet (for lists). : )