There's lots of measures: Indeed job listings, google searches, mailing list volume; tiobe tries to incorporate a few.
http://www.drewconway.com/zia/?p=2892
http://www.wired.com/wiredenterprise/2012/06/berkeley-progra...
I think "respective reputations" can be quite subjective. In my circles Haskell is definitely more talked about/used.
Sure: In the "hacker" world it seems that people prefer Haskell (Purely functional, native code) to Scala (OO Hybrid, JVM).
However I'd say that Scala is far more popular for building bussiness/real software than Haskell is (Twitter for example).
http://www.langpop.com/