Elevator pitch for Haskell short enough for an elevator ride

Greg Hale has written an "elevator pitch" for Haskell. While it is certainly a good piece of advocacy, it is quite long, and therefore not an elevator pitch. The idea of an elevator pitch is something you can deliver in the 30 seconds or so that you find yourself sharing an elevator with a potential investor.

I've been looking for an effective Haskell elevator pitch for some years now, but the only thing I was able to come up with was just that you can deliver software better, faster and cheaper because you need fewer lines of code. This just sounds like hype.

However I think I've now got something better. Here it is:

Conventional languages make the programmer construct both a control flow and a data flow for the program. There is no way to check they are consistent, and anytime they are inconsistent you get a bug. In Haskell the programmer just specifies the data flow: the control flow is up to the compiler. That simplifies the program, cutting down the work and completely preventing a big class of errors.