data - Cumulative percentage between 4 controls

I have a tricky request that requires the user being able to change the values across 4 vectors. The catch is that the four vectors between them must total 100%.

My initial thought is to go with 4 sliders.

This would mean that, as the total must be 100%, the user would have to lower one value before raising another. Is this intuitive enough?

Maybe some help text and a red/green label for values under 100% (red) and on 100% (green)?

If anybody has a more elegant solution for this I'd love to here it!

Answer

Ask yourself if it's the system or the user that's concerned with 1% accuracy. Does the user really want to think about the distributed percentages, or just the priority of each point?

If a high level of precision is purely the domain of the system, consider asking your users how much they care about each point on a relative scale. You can break that down on the back-end and calculate the percentage for them. No humans doing math.

So in this illustration ...

The user sees:

Low
Medium
High

The system sees:

"Meh" = ((1*20)*(100/((1*20)+(3*20)+(5*20))) = 11.11111%
"Sure" = ((3*20)*(100/((1*20)+(3*20)+(5*20))) = 33.33333%
"OMG!!!" = ((5*20)*(100/((1*20)+(3*20)+(5*20))) = 55.55555%

Easy for the user, easy for the computer. It's a perfect world!