Jobs requiring functional programming

If you want a job as a software developer, how useful is it to know functional programming languages?

To answer this question, I went to four employment sites and searched for four functional languages: Scala, Erlang, Clojure, and Haskell. For calibration, I also searched for three mainstream programming languages: Java, C++, and SQL. Two of the employment sites were Canadian (Workopolis and Monster.ca) and two were American (Monster.com and careers.joelonsoftware.com).

Workopolis:

Java     696
C++      282
SQL     1368
Scala      3
Erlang     2
Clojure    1
Haskell    1

Monster.ca:

Java     668
C++      288
SQL     1000+
Scala      2
Erlang     0
Clojure    0
Haskell    0

Monster.com:

Java    1000+
C++     1000+
SQL     1000+
Scala     72
Erlang    36
Clojure   12
Haskell   26

careers.joelonsoftware.com:

Java     252
C++      140
SQL      231
Scala     24
Erlang    11
Clojure    9
Haskell    9

Based on these figures, there are some jobs out there that call for functional-programming expertise, but not many, particularly compared to the number calling for mainstream imperative languages. And virtually none of them are in Canada.